diff --git a/.github/workflows/workflow.yml b/.github/workflows/workflow.yml
index 4f865fb4e..76030c564 100644
--- a/.github/workflows/workflow.yml
+++ b/.github/workflows/workflow.yml
@@ -17,30 +17,29 @@ jobs:
         ocaml-compiler:
           - 4.04.x
           - 4.05.x
-          - 4.06.x
-          - 4.07.x
-          - 4.08.x
-          - 4.09.x
-          - 4.10.x
           - 4.11.x
-          - 4.12.x
+          - 4.13.x
+          - 4.14.x
+          - 5.0.x
+          - 5.1.x
         include:
           - os: macos-latest
-            ocaml-compiler: 4.12.x
+            ocaml-compiler: 4.14.x
           - os: windows-latest
-            ocaml-compiler: 4.12.x
+            ocaml-compiler: 4.14.x
+          - os: macos-latest
+            ocaml-compiler: 5.1.x
 
     runs-on: ${{ matrix.os }}
 
     steps:
       - name: Checkout code
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
 
       - name: Use OCaml ${{ matrix.ocaml-compiler }}
         uses: ocaml/setup-ocaml@v2
         with:
           ocaml-compiler: ${{ matrix.ocaml-compiler }}
-          dune-cache: true
           opam-depext-flags: --with-test
 
       - run: opam install . --deps-only --with-test
diff --git a/CHANGES.md b/CHANGES.md
index 51542f7d0..8f2859210 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -1,4 +1,13 @@
-# NEXT
+# 4.6.0
+
+* Update for OCaml 5.0 and drop support for OCaml 4.2.0
+  (#312 by @rr0gi)
+
+* Add additional variants to `linktype` for the `rel` attribute
+  (Leon @LogicalOverflow Vack)
+
+* Expand options for `autocomplete` attribute on `<input>` elements
+  (#302 by Aron @aronerben Erben)
 
 * Fix the SVG animation attributes `a_animation_values`, `a_keyTimes` and `a_keySplines`
   to contain semicolon separated values.
@@ -10,10 +19,15 @@
 
 * Add support for `dialog` element and `onclose` attribute
   (#301 by Julien Sagot)
-
+* Add an escape hatch for emitting attributes with non-standard names
+  in jsx or ppx code (a leading `_` character on attribute name)
+  (#295 Chas @cemerick Emerick)
 * Add support for `type` attribute on `<script>` elements
   (#293 by Ulrik @ulrikstrid Strid and Chas @cemerick Emerick)
 
+* Add svg `fill-rule` attribute
+  (#294 by Eric @dedbox Griffis)
+
 # 4.5.0
 
 * Move all the PPXs to ppxlib
diff --git a/CODE_OF_CONDUCT.md b/CODE_OF_CONDUCT.md
new file mode 100644
index 000000000..738eab51f
--- /dev/null
+++ b/CODE_OF_CONDUCT.md
@@ -0,0 +1,12 @@
+# Code of Conduct
+
+This project has adopted the [OCaml Code of Conduct](https://github.com/ocaml/code-of-conduct/blob/main/CODE_OF_CONDUCT.md).
+
+# Enforcement
+
+This project follows the OCaml Code of Conduct [enforcement policy](https://github.com/ocaml/code-of-conduct/blob/main/CODE_OF_CONDUCT.md#enforcement).
+
+To report any violations, please contact Jérôme
+Vouillon, Raphael Proust, Vincent Balat, Hugo Heuzard and Gabriel
+Radanne at <moderation [at] ocsigen [dot] org>
+(or some of them individually).
diff --git a/docs/manual-wiki/jsx.wiki b/docs/manual-wiki/jsx.wiki
index f7dc2d290..0333b37fa 100644
--- a/docs/manual-wiki/jsx.wiki
+++ b/docs/manual-wiki/jsx.wiki
@@ -80,6 +80,27 @@ version in <<a_api project="js_of_ocaml" subproject="js_of_ocaml-tyxml" | Js_of_
 
 In each case, simply open the module and the JSX syntax will use it.
 
+==@@id="unsafe"@@ "Unsafe" attributes
+
+Some Javascript libraries and frameworks depend upon HTML markup that includes non-standard
+attributes, which tyxml would usually reject. When constructing elements using tyxml's API directly,
+the available workaround is to use the <<a_api text="Unsafe"|val Html_sigs.T.Unsafe>> constructors.
+The same relaxed semantics can be had when using JSX by prefixing non-standard attribute names
+with a leading underscore.
+
+So, while this will fail:
+<<code language="ocaml"|
+let button = <button hx_post="/clicked" hx_swap="outerHTML">Click Me</button>
+>>
+
+This will not:
+<<code language="ocaml"|
+let button = <button _hx_post="/clicked" _hx_swap="outerHTML">Click Me</button>
+>>
+
+Such underscore-prefixed attributes are presumed to be strings, and are constructed using e.g.
+<<a_api text="Unsafe.string_attrib"|val Html_sigs.T.Unsafe.string_attrib>>.
+
 ==@@id="tips"@@ Tips
 
 It can sometime be necessary to disable the JSX syntax. For that purpose, simply use the toogle `[@tyxml.jsx false]` to turn the JSX on and off.
diff --git a/docs/manual-wiki/ppx.wiki b/docs/manual-wiki/ppx.wiki
index ab1326c98..1e2d1923b 100644
--- a/docs/manual-wiki/ppx.wiki
+++ b/docs/manual-wiki/ppx.wiki
@@ -59,6 +59,27 @@ let my_div = [%html "<div id="my_id"></div>"]
 val my_div : [> Html_types.div ] Html.elt
 >>
 
+==@@id="unsafe"@@ "Unsafe" attributes
+
+Some Javascript libraries and frameworks depend upon HTML markup that includes non-standard
+attributes, which tyxml would usually reject. When constructing elements using tyxml's API directly,
+the available workaround is to use the <<a_api text="Unsafe"|val Html_sigs.T.Unsafe>> constructors.
+The same relaxed semantics can be had when using the ppx by prefixing non-standard attribute names
+with a leading underscore.
+
+So, while this will fail:
+<<code language="ocaml"|
+[%html {|<button hx_post="/clicked" hx_swap="outerHTML">Click Me</button>|}]
+>>
+
+This will not:
+<<code language="ocaml"|
+[%html {|<button _hx_post="/clicked" _hx_swap="outerHTML">Click Me</button>|}]
+>>
+
+Such underscore-prefixed attributes are presumed to be strings, and are constructed using e.g.
+<<a_api text="Unsafe.string_attrib"|val Html_sigs.T.Unsafe.string_attrib>>.
+
 ==@@id="let"@@ Let notation
 
 It is also possible to use the ppx with the ##let## notation:
diff --git a/dune-project b/dune-project
index 43ccc863b..0decfd1b8 100644
--- a/dune-project
+++ b/dune-project
@@ -60,7 +60,7 @@
  (synopsis "Common layer for the JSX and PPX syntaxes for Tyxml")
  (depends
   (ocaml
-   (>= 4.02))
+   (>= 4.03))
   (alcotest :with-test)
   (ppxlib
    (>= 0.18))
@@ -76,7 +76,7 @@
    "TyXML provides a set of convenient combinators that uses the OCaml type system to ensure the validity of the generated documents. TyXML can be used with any representation of HTML and SVG: the textual one, provided directly by this package, or DOM trees (`js_of_ocaml-tyxml`) virtual DOM (`virtual-dom`) and reactive or replicated trees (`eliom`). You can also create your own representation and use it to instantiate a new set of combinators.")
  (depends
   (ocaml
-   (>= 4.02))
+   (>= 4.03))
   (alcotest :with-test)
   (re
    (>= 1.5.0))
diff --git a/jsx/dune b/jsx/dune
index 90f709dfc..31a02b766 100644
--- a/jsx/dune
+++ b/jsx/dune
@@ -11,4 +11,4 @@
          -open Ppxlib
          -w "-9"
  ))
-)
+)
\ No newline at end of file
diff --git a/jsx/tyxml_jsx.ml b/jsx/tyxml_jsx.ml
index 1b47b9892..42c2476a8 100644
--- a/jsx/tyxml_jsx.ml
+++ b/jsx/tyxml_jsx.ml
@@ -9,30 +9,30 @@ let is_jsx e =
   in
   List.exists f e.pexp_attributes
 
-(* When dropping support for 4.02, this module can simply be deleted. *)
-module String = struct
-  include String
-  let lowercase_ascii = String.lowercase [@ocaml.warning "-3"]
-end
-module Char = struct
-  include Char
-  let lowercase_ascii = Char.lowercase [@ocaml.warning "-3"]
-end
-
 let lowercase_lead s =
   String.mapi (fun i c -> if i = 0 then Char.lowercase_ascii c else c) s
 
-let to_kebab_case name =
-  let length = String.length name in
-  if length > 5 then
-    let first = String.sub name 0 4 in
-    match first with
-    | "aria"
-    | "data" ->
-      first ^ "-" ^ lowercase_lead (String.sub name 4 (length - 4))
-    | _ -> name
-  else
-    name
+let to_kebab_case =
+  let open Re in
+  let camelPat = Posix.compile_pat "[A-Z]" in
+  let underscore = compile @@ char '_' in
+  let prefixes = Perl.compile_pat {|^(data_?|aria_?)(.+)|} in
+  fun name ->
+    let kebab string =
+      replace camelPat ~f:(fun g -> "-" ^ Group.get g 0) string
+      |> String.lowercase_ascii
+      |> replace_string underscore ~by:"-" in
+    match exec_opt prefixes name with
+    | None -> 
+      if name.[0] == '_'
+      (* need to keep the leading underscore, as that's what the syntax support keys
+         off of to know to use Unsafe.string_attrib *)
+      then "_" ^ kebab @@ String.sub name 1 (String.length name - 1)
+      else name
+    | Some g ->
+      let prefix = String.sub name 0 4 in
+      let suffix = kebab @@ Group.get g 2 in
+      prefix ^ (if suffix.[0] == '-' then "" else "-") ^ suffix
 
 let make_attr_name name =
   let name =
diff --git a/lib/html_f.ml b/lib/html_f.ml
index 905100663..4e1484f99 100644
--- a/lib/html_f.ml
+++ b/lib/html_f.ml
@@ -56,7 +56,6 @@ struct
     | `Url_width of uri * Html_types.number
     | `Url_pixel of uri * Html_types.float_number ]
 
-
   type 'a attrib = Xml.attrib
 
   let to_xmlattribs x = x
@@ -256,7 +255,7 @@ struct
   let a_method x =
     user_attrib C.string_of_big_variant "method" x
 
-  let a_formmethod = a_method
+  let a_formmethod x = user_attrib C.string_of_big_variant "formmethod" x
 
   let a_enctype = string_attrib "enctype"
 
@@ -285,7 +284,7 @@ struct
     user_attrib C.string_of_referrerpolicy "referrerpolicy" x
 
   let a_autocomplete x =
-    user_attrib C.onoff_of_bool "autocomplete" x
+    user_attrib C.string_of_autocomplete "autocomplete" x
 
   let a_async =
     constant_attrib "async"
@@ -887,6 +886,7 @@ struct
     | `Author -> "author"
     | `Bookmark -> "bookmark"
     | `Canonical -> "canonical"
+    | `Dns_prefetch -> "dns-prefetch"
     | `External -> "external"
     | `First -> "first"
     | `Help -> "help"
@@ -894,12 +894,19 @@ struct
     | `Index -> "index"
     | `Last -> "last"
     | `License -> "license"
+    | `Manifest -> "manifest"
+    | `Me -> "me"
+    | `Modulepreload -> "modulepreload"
     | `Next -> "next"
     | `Nofollow -> "nofollow"
-    | `Noreferrer -> "noreferrer"
     | `Noopener -> "noopener"
+    | `Noreferrer -> "noreferrer"
+    | `Opener -> "opener"
     | `Pingback -> "pingback"
+    | `Preconnect -> "preconnect"
     | `Prefetch -> "prefetch"
+    | `Preload -> "preload"
+    | `Prerender -> "prerender"
     | `Prev -> "prev"
     | `Search -> "search"
     | `Stylesheet -> "stylesheet"
@@ -1121,6 +1128,12 @@ struct
     in
     String.concat ", " (List.map f l)
 
+  let string_of_autocomplete (l : Html_types.autocomplete_option) =
+    match l with
+    | `On | `Tokens [] -> "on"
+    | `Off -> "off"
+    | `Tokens strs -> String.concat " " strs
+
 end
 
 module Make
diff --git a/lib/html_sigs.mli b/lib/html_sigs.mli
index 2f0a9debd..1cf169c8f 100644
--- a/lib/html_sigs.mli
+++ b/lib/html_sigs.mli
@@ -261,7 +261,8 @@ module type T = sig
 
   val a_allowpaymentrequest : unit -> [> | `Allowpaymentrequest] attrib
 
-  val a_autocomplete : (bool[@onoff]) wrap -> [> | `Autocomplete] attrib
+  val a_autocomplete : autocomplete_option wrap -> [> | `Autocomplete] attrib
+  (** @see <https://developer.mozilla.org/en-US/docs/Web/HTML/Attributes/autocomplete> autocomplete documentation. *)
 
   val a_async : unit -> [> | `Async] attrib
 
@@ -502,9 +503,7 @@ module type T = sig
     [< | `Get | `Post] wrap -> [> | `Method] attrib
 
   val a_formmethod :
-    [< | `Get | `Post] wrap -> [> | `Method] attrib
-  [@@ocaml.deprecated "Use a_method"]
-  (** @deprecated Use a_method *)
+    [< | `Get | `Post] wrap -> [> | `Formmethod] attrib
 
   val a_multiple : unit -> [> | `Multiple] attrib
 
@@ -1011,6 +1010,7 @@ module type T = sig
 
   val textarea :
     ([< | textarea_attrib], [< | textarea_content_fun], [> | textarea]) unary
+  [@@reflect.element "textarea"]
 
   val keygen : ([< | keygen_attrib], [> | keygen]) nullary
 
@@ -1255,6 +1255,9 @@ module type Wrapped_functions = sig
   val string_of_srcset :
     ([< image_candidate] list, string) Xml.W.ft
 
+  val string_of_autocomplete :
+    (Html_types.autocomplete_option, string) Xml.W.ft
+
   val string_of_step : (float option, string) Xml.W.ft
 
   val unoption_string : (string option, string) Xml.W.ft
diff --git a/lib/html_types.mli b/lib/html_types.mli
index f28ff3713..7ccd3d3cc 100644
--- a/lib/html_types.mli
+++ b/lib/html_types.mli
@@ -108,6 +108,7 @@ type linktype =
     | `Author
     | `Bookmark
     | `Canonical
+    | `Dns_prefetch
     | `External
     | `First
     | `Help
@@ -115,13 +116,20 @@ type linktype =
     | `Index
     | `Last
     | `License
+    | `Manifest
+    | `Me
+    | `Modulepreload
     | `Next
     | `Nofollow
-    | `Noreferrer
     | `Noopener
+    | `Noreferrer
+    | `Opener
     | `Pingback
+    | `Preconnect
     | `Prefetch
     | `Prev
+    | `Preload
+    | `Prerender
     | `Search
     | `Stylesheet
     | `Sidebar
@@ -151,6 +159,8 @@ type linktypes = linktype list
         Gives the permalink for the nearest ancestor section.}
         {- [`Canonical]:
         Gives the preferred location for accessing the current document.}
+        {- [`Dns_prefetch]:
+        Specifies that the user agent should preemptively perform DNS resolution for the target resource's origin..}
         {- [`External]:
         Indicates that the referenced document is not part of the same site as the current document.}
         {- [`First]:
@@ -165,18 +175,32 @@ type linktypes = linktype list
         Indicates that the current document is a part of a series, and that the last document in the series is the referenced document.}
         {- [`Licence]:
         Indicates that the main content of the current document is covered by the copyright license described by the referenced document.}
+        {- [`Manifest]:
+        Imports or links to an application manifest.}
+        {- [`Me]:
+        Indicates that the current document represents the person who owns the linked content.}
+        {- [`Modulepreload]:
+        Specifies that the user agent must preemptively fetch the module script and store it in the document's module map for later evaluation. Optionally, the module's dependencies can be fetched as well.}
         {- [`Next]:
         Indicates that the current document is a part of a series, and that the next document in the series is the referenced document.}
         {- [`Nofollow]:
         Indicates that the current document's original author or publisher does not endorse the referenced document.}
-        {- [`Noreferrer]:
-        Requires that the user agent not send an HTTP Referer (sic) header if the user follows the hyperlink.}
         {- [`Noopener]:
         Instructs the browser to open the link without granting the new browsing context access to the document that opened it.}
+        {- [`Noreferrer]:
+        Requires that the user agent not send an HTTP Referer (sic) header if the user follows the hyperlink.}
+        {- [`Opener]:
+        Creates an auxiliary browsing context if the hyperlink would otherwise create a top-level traversable with a non-auxiliary browsing context (i.e., has "_blank" as target attribute value).}
         {- [`Pingback]:
         Gives the address of the pingback server that handles pingbacks to the current document.}
+        {- [`Preconnect]:
+        Specifies that the user agent should preemptively connect to the target resource's origin.}
         {- [`Prefetch]:
         Specifies that the target resource should be preemptively cached.}
+        {- [`Preload]:
+        Specifies that the user agent must preemptively fetch and cache the target resource for current navigation according to the potential destination given by the as attribute (and the priority associated with the corresponding destination).}
+        {- [`Prerender]:
+        Specifies that the user agent should preemptively fetch the target resource and process it in a way that helps deliver a faster response in the future.}
         {- [`Prev]:
         Indicates that the current document is a part of a series, and that the previous document in the series is the referenced document.}
         {- [`Search]:
@@ -1854,7 +1878,7 @@ type source_content = notag
 
 type source_content_fun = notag
 
-type source_attrib = [ | common | `Src | `Mime_type | `Media ]
+type source_attrib = [ | common | `Src | `Srcset | `Mime_type | `Media ]
 
 (* NAME: area, KIND: nullary, TYPE: [= common | `Alt | `Coords | `Shape| `Target | `Rel | `Media| `Hreflang | `Mime_type],[=`Area], ARG: notag, ATTRIB:  OUT: [=`Area] *)
 type area = [ | `Area ]
@@ -2050,8 +2074,9 @@ type input_attrib =
     | `Checked
     | `Disabled
     | `Form
-    | `Formation
+    | `Formaction
     | `Formenctype
+    | `Formmethod
     | `Method
     | `Formnovalidate
     | `Formtarget
@@ -2114,6 +2139,7 @@ type button_attrib =
     | `Form
     | `Formaction
     | `Formenctype
+    | `Formmethod
     | `Method
     | `Formnovalidate
     | `Formtarget
@@ -2429,3 +2455,5 @@ type input_type =
   | `Week ]
 
 type script_type = [ `Javascript | `Module | `Mime of string ]
+
+type autocomplete_option = [ `On | `Off | `Tokens of string list]
diff --git a/lib/svg_f.ml b/lib/svg_f.ml
index b911ff8b9..96273f239 100644
--- a/lib/svg_f.ml
+++ b/lib/svg_f.ml
@@ -101,6 +101,10 @@ let string_of_paint = function
     (string_of_iri iri) ^" "^ (string_of_paint_whitout_icc b)
   | #paint_whitout_icc as c -> string_of_paint_whitout_icc c
 
+let string_of_fill_rule = function
+  | `Nonzero -> "nonzero"
+  | `Evenodd -> "evenodd"
+
 module Make_with_wrapped_functions
 
     (Xml : Xml_sigs.T)
@@ -535,6 +539,8 @@ struct
   let a_animation_fill x =
     user_attrib C.string_of_big_variant "fill" x
 
+  let a_fill_rule = user_attrib C.string_of_fill_rule "fill-rule"
+
   let a_calcMode x =
     user_attrib C.string_of_big_variant "calcMode" x
 
@@ -1108,6 +1114,8 @@ struct
 
   let string_of_paint = string_of_paint
 
+  let string_of_fill_rule = string_of_fill_rule
+
   let string_of_strokedasharray = function
     | [] -> "none"
     | l -> list string_of_length l
diff --git a/lib/svg_sigs.mli b/lib/svg_sigs.mli
index 4c04b671c..94bf76ed7 100644
--- a/lib/svg_sigs.mli
+++ b/lib/svg_sigs.mli
@@ -275,7 +275,7 @@ module type T = sig
     [< `UserSpaceOnUse | `ObjectBoundingBox ] wrap ->
     [ | `GradientUnits ] attrib
 
-  val a_gradientTransform : transforms wrap -> [> | `Gradient_Transform ] attrib
+  val a_gradientTransform : transforms wrap -> [> | `GradientTransform ] attrib
 
   val a_spreadMethod :
     [< `Pad | `Reflect | `Repeat ] wrap -> [> | `SpreadMethod ] attrib
@@ -488,6 +488,8 @@ module type T = sig
   val a_animation_fill : [< | `Freeze | `Remove ] wrap -> [> | `Fill_Animation ] attrib
     [@@reflect.attribute "fill" ["animate"]]
 
+  val a_fill_rule : fill_rule wrap -> [> | `Fill_rule ] attrib
+
   val a_calcMode :
     [< | `Discrete | `Linear | `Paced | `Spline ] wrap -> [> | `CalcMode ] attrib
 
@@ -1110,6 +1112,8 @@ module type Wrapped_functions = sig
   val string_of_orient : (Svg_types.Unit.angle option, string) Xml.W.ft
 
   val string_of_paint : ([< Svg_types.paint], string) Xml.W.ft
+  
+  val string_of_fill_rule : ([< Svg_types.fill_rule], string) Xml.W.ft
 
   val string_of_strokedasharray : (Svg_types.lengths, string) Xml.W.ft
 
diff --git a/lib/svg_types.mli b/lib/svg_types.mli
index 604f2ae60..a786da522 100644
--- a/lib/svg_types.mli
+++ b/lib/svg_types.mli
@@ -288,6 +288,10 @@ type paint =
   [ paint_whitout_icc
   | `Icc of (iri * paint_whitout_icc option) ]
 
+type fill_rule =
+  [ `Nonzero
+  | `Evenodd ]
+
 (* Transformation *)
 type transform =
   [ `Matrix of (float * float * float * float * float * float)
diff --git a/ppx/tyxml_ppx.ml b/ppx/tyxml_ppx.ml
index a5ff80d12..5319c1236 100644
--- a/ppx/tyxml_ppx.ml
+++ b/ppx/tyxml_ppx.ml
@@ -19,12 +19,6 @@
 
 open Tyxml_syntax
 
-(* When dropping support for 4.02, this module can simply be deleted. *)
-module String = struct
-  include String
-  let capitalize_ascii = String.capitalize [@ocaml.warning "-3"]
-end
-
 open Ppxlib.Asttypes
 open Ppxlib.Parsetree
 
diff --git a/syntax/attribute_value.ml b/syntax/attribute_value.ml
index 2de50fc24..4630d6e11 100644
--- a/syntax/attribute_value.ml
+++ b/syntax/attribute_value.ml
@@ -484,6 +484,17 @@ let paint ?separated_by:_ ?default:_ loc name s =
             `Icc ([%e iri], Some [%e paint_without_icc loc name remainder])]
     end [@metaloc loc]
 
+let fill_rule ?separated_by:_ ?default:_ loc _name s =
+  begin match s with
+  | "nonzero" ->
+    Some [%expr `Nonzero]
+  
+  | "evenodd" ->
+    Some [%expr `Evenodd]
+
+  | _ -> None
+  end [@metaloc loc]
+
 let srcset_element =
   let space = Re_str.regexp " +" in
 
@@ -540,6 +551,17 @@ let number_or_datetime ?separated_by:_ ?default:_ loc _ s =
   | None -> Some [%expr `Datetime [%e Common.string loc s]]
   [@metaloc loc]
 
+let autocomplete ?separated_by:_ ?default:_ loc name s =
+  match s with
+  | "on" | "" -> Some [%expr `On]
+  | "off" -> Some [%expr `Off]
+  | tks ->
+    match spaces (string) loc name tks with
+      | Some tks -> Some [%expr `Tokens [%e tks]]
+      | None -> Common.error loc "Bad autocomplete tokens"
+  [@metaloc loc]
+
+
 let script_type =
   (* According to https://developer.mozilla.org/en-US/docs/Web/HTML/Element/script, non-javascript
      MIME types are allowed, but then denotes the <script> content as a "data block" (whatever that
diff --git a/syntax/attribute_value.mli b/syntax/attribute_value.mli
index a8be09b83..339afa6bd 100644
--- a/syntax/attribute_value.mli
+++ b/syntax/attribute_value.mli
@@ -198,9 +198,18 @@ val paint : parser
    {:{https://www.w3.org/TR/SVG/painting.html#SpecifyingPaint} Specifying
    paint}. *)
 
+val fill_rule : parser
+(** Parses an SVG fill-rule value.
+
+    @see <https://developer.mozilla.org/en-US/docs/Web/SVG/Attribute/fill-rule>
+*)
+
 val srcset_element : parser
 (** Used for [a_srcset]. *)
 
+val autocomplete : parser
+(** Used for [a_autocomplete]. *)
+
 val number_or_datetime : parser
 (** Used for [a_input_min] and [a_input_max]. *)
 
diff --git a/syntax/attributes.ml b/syntax/attributes.ml
index 678dec5a0..85177bf2d 100644
--- a/syntax/attributes.ml
+++ b/syntax/attributes.ml
@@ -104,15 +104,23 @@ let parse loc (language, element_name) attributes =
           labeled, e::regular
         in
 
-        (* Check if this is a "data-foo" or "aria-foo" attribute. Parse the
-           attribute value, and accumulate it in the list of attributes passed
+        (* Check if this is a "data-foo", "aria-foo", or unsafe attribute. Parse
+           the attribute value, and accumulate it in the list of attributes passed
            in ~a. *)
         match parse_prefixed "data-" local_name,
-              parse_prefixed "aria-" local_name
+              parse_prefixed "aria-" local_name,
+              parse_prefixed "_" local_name
         with
-        | Some tag, _ -> parse_prefixed_attribute tag "a_user_data"
-        | _, Some tag -> parse_prefixed_attribute tag "a_aria"
-        | None, None ->
+        | Some tag, _, _ -> parse_prefixed_attribute tag "a_user_data"
+        | _, Some tag, _ -> parse_prefixed_attribute tag "a_aria"
+        | _, _, Some tag ->
+          let identifier = Common.make ~loc language "Unsafe.string_attrib" in
+          let tag = Common.string loc tag in
+          let value = match value with
+                      | Val s -> Common.string loc s
+                      | Antiquot v -> v in
+          labeled, [%expr [%e identifier] [%e tag] [%e value]] :: regular
+        | None, None, None ->
           let tyxml_name =
             match Common.find test_renamed Reflected.renamed_attributes with
             | Some (name, _, _) -> name
diff --git a/syntax/element_content.ml b/syntax/element_content.ml
index 3f364fd86..8a352cc75 100644
--- a/syntax/element_content.ml
+++ b/syntax/element_content.ml
@@ -218,7 +218,7 @@ let datalist ~lang ~loc ~name children =
   children::(nullary ~lang ~loc ~name [])
 
 
-let script ~lang ~loc ~name children =
+let at_most_one_child ~lang ~loc ~name children =
   match children with
   | [] ->
     let child = Common.txt ~loc ~lang "" in
@@ -228,6 +228,11 @@ let script ~lang ~loc ~name children =
     [Nolabel, child]
   | _ -> Common.error loc "%s can have at most one child" name
 
+let script = at_most_one_child
+
+(* https://html.spec.whatwg.org/#the-textarea-element *)
+let textarea = at_most_one_child
+
 let details ~lang ~loc ~name children =
   let summary, others = partition (html "summary") children in
 
diff --git a/syntax/element_content.mli b/syntax/element_content.mli
index 17b53af9c..ec88768f2 100644
--- a/syntax/element_content.mli
+++ b/syntax/element_content.mli
@@ -79,6 +79,7 @@ val details : assembler
 val menu : assembler
 val picture : assembler
 val script : assembler
+val textarea : assembler
 
 (** {1 Misc utilities} *)
 
diff --git a/syntax/name_convention.ml b/syntax/name_convention.ml
index 3dd3abd3c..419d5911f 100644
--- a/syntax/name_convention.ml
+++ b/syntax/name_convention.ml
@@ -4,13 +4,6 @@
    see <http://www.w3.org/TR/html51/syntax.html#syntax>
 *)
 
-(* When dropping support for 4.02, this module can simply be deleted. *)
-module Char = struct
-  include Char
-  let lowercase_ascii = Char.lowercase [@ocaml.warning "-3"]
-  let uppercase_ascii = Char.uppercase [@ocaml.warning "-3"]
-end
-
 (* In the ocaml parser:
    let identchar = ['A'-'Z' 'a'-'z' '_' '\'' '0'-'9']
 *)
diff --git a/syntax/reflect/reflect.ml b/syntax/reflect/reflect.ml
index 79d07c2cd..dafd1975b 100644
--- a/syntax/reflect/reflect.ml
+++ b/syntax/reflect/reflect.ml
@@ -211,6 +211,9 @@ let rec to_attribute_parser lang name ~loc = function
   | [[%type: image_candidate list]] ->
     [%expr commas srcset_element]
 
+  | [[%type: autocomplete_option]] ->
+    [%expr autocomplete]
+
   | _ ->
     let name = strip_a name in
     let name = if name = "in" then "in_" else name in
diff --git a/test/test_html.ml b/test/test_html.ml
index 51fdb5fe2..c64d4f1c5 100644
--- a/test/test_html.ml
+++ b/test/test_html.ml
@@ -10,6 +10,10 @@ let html_elements = "html elements", tyxml_tests Html.[
   div [a []],
   "<div><a></a></div>" ;
 
+  "input",
+  input ~a:[a_formaction "post.html"; a_formmethod `Post] (),
+  "<input formaction=\"post.html\" formmethod=\"POST\"/>";
+
   "a",
   canvas [a []],
   "<canvas><a></a></canvas>";
@@ -17,8 +21,7 @@ let html_elements = "html elements", tyxml_tests Html.[
   "template",
   template ~a:[a_id "idtmpl"] [p [txt "Template"]],
   "<template id=\"idtmpl\"><p>Template</p></template>" ;
-
-  "picture",
+  "picture_src",
   div [
     picture ~a:[a_id "idpicture"]
       ~img:(img ~a:[a_id "idimg"] ~src:"picture/img.png" ~alt:"test picture/img.png" ()) [
@@ -30,6 +33,22 @@ let html_elements = "html elements", tyxml_tests Html.[
     ^ {|<source type="image/webp" src="picture/img1.webp"/>|}
     ^ {|<source type="image/jpeg" src="picture/img2.jpg"/>|}
     ^ {|<img src="picture/img.png" alt="test picture/img.png" id="idimg"/>|}
+    ^ {|</picture></div>|} ;
+
+  "picture_srcset",
+  div [
+    picture ~a:[a_id "idpicture"]
+      ~img:(img ~a:[a_id "idimg"] ~src:"picture/img.png" ~alt:"test picture/img.png" ()) [
+      source ~a:[a_mime_type "image/webp";
+                 a_srcset [`Url (Xml.uri_of_string "picture/img1.webp")]] ()
+    ; source ~a:[a_mime_type "image/jpeg";
+                 a_srcset [`Url (Xml.uri_of_string "picture/img2.jpg")]] ()
+    ]
+  ],
+  {|<div><picture id="idpicture">|}
+    ^ {|<source type="image/webp" srcset="picture/img1.webp"/>|}
+    ^ {|<source type="image/jpeg" srcset="picture/img2.jpg"/>|}
+    ^ {|<img src="picture/img.png" alt="test picture/img.png" id="idimg"/>|}
   ^ {|</picture></div>|} ;
 ]
 
diff --git a/test/test_jsx.re b/test/test_jsx.re
index 854f55895..18a5d4a7c 100644
--- a/test/test_jsx.re
+++ b/test/test_jsx.re
@@ -106,17 +106,45 @@ let attribs = (
         [<div draggable=false />],
         [div(~a=[a_draggable(false)], [])],
       ),
-      ( "onoff default",
+      ( "form autocomplete default is on",
         [<form autocomplete="" />],
-        [form(~a=[a_autocomplete(true)], [])],
+        [form(~a=[a_autocomplete(`On)], [])],
       ),
-      ( "bool true",
+      ( "form autocomplete on",
         [<form autocomplete="on" />],
-        [form(~a=[a_autocomplete(true)], [])],
+        [form(~a=[a_autocomplete(`On)], [])],
       ),
-      ( "bool false",
+      ( "form autocomplete off",
         [<form autocomplete="off" />],
-        [form(~a=[a_autocomplete(false)], [])],
+        [form(~a=[a_autocomplete(`Off)], [])],
+      ),
+      ( "form autocomplete tokenlist",
+        [<form autocomplete="section-blue shipping street-address" />],
+        [form(~a=[a_autocomplete(`Tokens(["section-blue", "shipping", "street-address"]))], [])],
+      ),
+      ( "form autocomplete tokenlist empty",
+        [<form autocomplete="on" />],
+        [form(~a=[a_autocomplete(`Tokens([]))], [])],
+      ),
+      ( "input autocomplete default is on",
+        [<input autocomplete="" />],
+        [input(~a=[a_autocomplete(`On)], ())],
+      ),
+      ( "input autocomplete on",
+        [<input autocomplete="on" />],
+        [input(~a=[a_autocomplete(`On)], ())],
+      ),
+      ( "input autocomplete off",
+        [<input autocomplete="off" />],
+        [input(~a=[a_autocomplete(`Off)], ())],
+      ),
+      ( "input autocomplete tokenlist",
+        [<input autocomplete="section-blue shipping street-address" />],
+        [input(~a=[a_autocomplete(`Tokens(["section-blue", "shipping", "street-address"]))], ())],
+      ),
+      ( "input autocomplete tokenlist empty",
+        [<input autocomplete="on" />],
+        [input(~a=[a_autocomplete(`Tokens([]))], ())],
       ),
       ( "link rel=canonical",
         [<link rel=[`Canonical] href="/" />],
@@ -158,7 +186,32 @@ let attribs = (
         [<script type_="text/javascript" />],
         [script(~a=[a_script_type(`Mime("text/javascript"))], txt(""))],
       ),
-    ],
+      ( "camel-case data attribs",
+        [<div dataFooBar="baz"/>],
+        // the Xml.W.nil is here to satisfy the internal structure of what the jsx ppx produces
+        [div(~a=[a_user_data("foo-bar", "baz")], Xml.W.nil ())],
+      ),
+      ( "kebab-case data attribs",
+        [<div data_foo_bar="baz"/>],
+        // the Xml.W.nil is here to satisfy the internal structure of what the jsx ppx produces
+        [div(~a=[a_user_data("foo-bar", "baz")], Xml.W.nil ())],
+      ),
+      ( "kebab-case data attribs, again",
+        [<div datafoo_bar="baz"/>],
+        // the Xml.W.nil is here to satisfy the internal structure of what the jsx ppx produces
+        [div(~a=[a_user_data("foo-bar", "baz")], Xml.W.nil ())],
+      ),
+      ( "arbitrary (unchecked) attributes via an escape hatch",
+        [<div _some_attr="value"/>],
+        // the Xml.W.nil is here to satisfy the internal structure of what the jsx ppx produces
+        [div(~a=[Unsafe.string_attrib("some-attr", "value")], Xml.W.nil ())],
+      ),
+      ( "arbitrary (unchecked) attributes via an escape hatch, with antiquotation",
+        [<div _some_attr={"val" ++ "ue"}/>],
+        // the Xml.W.nil is here to satisfy the internal structure of what the jsx ppx produces
+        [div(~a=[Unsafe.string_attrib("some-attr", "value")], Xml.W.nil ())],
+      ),
+    ]
   ),
 );
 
@@ -278,6 +331,16 @@ let svg = (
           ),
         ],
       ),
+      (
+        "fill_rule nonzero",
+        [<path fill_rule="nonzero" />],
+        [path(~a=[a_fill_rule(`Nonzero)], [])],
+      ),
+      (
+        "fill_rule evenodd",
+        [<path fill_rule="evenodd" />],
+        [path(~a=[a_fill_rule(`Evenodd)], [])],
+      ),
     ],
   ),
 );
diff --git a/test/test_ppx.ml b/test/test_ppx.ml
index 5218a23fd..b521aada4 100644
--- a/test/test_ppx.ml
+++ b/test/test_ppx.ml
@@ -211,6 +211,14 @@ let basics = "ppx basics", HtmlTests.make Html.[
   [[%html {|<script type="text/javascript"></script>|}]],
   [script ~a:[a_script_type (`Mime "text/javascript")] @@ txt ""];
 
+  "script empty",
+  [[%html {|<script></script>|}]],
+  [script @@ txt ""];
+
+  "textarea empty",
+  [[%html {|<textarea></textarea>|}]],
+  [textarea @@ txt ""];
+
 ]
 
 let attribs = "ppx attribs", HtmlTests.make Html.[
@@ -235,17 +243,45 @@ let attribs = "ppx attribs", HtmlTests.make Html.[
   [[%html "<div draggable=false></div>"]],
   [div ~a:[a_draggable false] []] ;
 
-  "onoff default",
+  "form autocomplete default is on",
   [[%html "<form autocomplete></form>"]],
-  [form ~a:[a_autocomplete true] []] ;
+  [form ~a:[a_autocomplete `On] []] ;
 
-  "bool true",
+  "form autocomplete on",
   [[%html "<form autocomplete=on></form>"]],
-  [form ~a:[a_autocomplete true] []] ;
+  [form ~a:[a_autocomplete `On] []] ;
 
-  "bool false",
+  "form autocomplete off",
   [[%html "<form autocomplete=off></form>"]],
-  [form ~a:[a_autocomplete false] []] ;
+  [form ~a:[a_autocomplete `Off] []] ;
+
+  "form autocomplete tokenlist",
+  [[%html "<form autocomplete='section-blue shipping street-address'></form>"]],
+  [form ~a:[a_autocomplete (`Tokens ["section-blue"; "shipping"; "street-address"] )] []] ;
+
+  "form autocomplete tokenlist empty",
+  [[%html "<form autocomplete=on></form>"]],
+  [form ~a:[a_autocomplete (`Tokens [] )] []] ;
+
+  "input autocomplete default is on",
+  [[%html "<input autocomplete/>"]],
+  [input ~a:[a_autocomplete `On] ()] ;
+  
+  "input autocomplete on",
+  [[%html "<input autocomplete='on'/>"]],
+  [input ~a:[a_autocomplete `On] ()] ;
+  
+  "input autocomplete off",
+  [[%html "<input autocomplete='off'/>"]],
+  [input~a:[a_autocomplete `Off] ()] ;
+  
+  "input autocomplete tokenlist",
+  [[%html "<input autocomplete='section-blue shipping street-address'/>"]],
+  [input ~a:[a_autocomplete (`Tokens ["section-blue"; "shipping"; "street-address"] )] ()] ;
+  
+  "input autocomplete tokenlist empty",
+  [[%html "<input autocomplete='on'/>"]],
+  [input ~a:[a_autocomplete (`Tokens [] )] ()] ;
 
   "link rel=canonical",
   [[%html "<link rel=canonical href='/'>"]],
@@ -283,6 +319,12 @@ let attribs = "ppx attribs", HtmlTests.make Html.[
   [[%html "<div data-foo='valfoo'></div>"]],
   [div
     ~a:[a_user_data "foo" "valfoo"] []] ;
+  
+  "arbitrary (unchecked) attributes via an escape hatch",
+  [[%html "<div _some-attr='value'></div>"]],
+  [div
+    ~a:[Unsafe.string_attrib "some-attr" "value"] []]
+      
 ]
 
 let ns_nesting = "namespace nesting" , HtmlTests.make Html.[
@@ -374,6 +416,14 @@ let svg = "svg", SvgTests.make Svg.[
   [[%svg "<animate fill='freeze' values='1 2'/>"]],
   [animate ~a:[a_animation_fill `Freeze; a_animation_values ["1"; "2"]] []] ;
 
+  "fill_rule type nonzero",
+  [[%svg "<path fill-rule='nonzero'/>"]],
+  [path ~a:[a_fill_rule `Nonzero] []] ;
+
+  "fill_rule type evenodd",
+  [[%svg "<path fill-rule='evenodd'/>"]],
+  [path ~a:[a_fill_rule `Evenodd] []] ;
+
 ]
 
 let svg_element_names = "svg element names", SvgTests.make Svg.[
diff --git a/test/test_svg.ml b/test/test_svg.ml
index 5c574db1e..0e158a7ac 100644
--- a/test/test_svg.ml
+++ b/test/test_svg.ml
@@ -1,9 +1,8 @@
 open Tyxml
 
-let to_string = Format.asprintf "%a" (Svg.pp_elt ())
-
 let tyxml_tests l =
-  let f (name, (ty : Svg_types.text Svg.elt), s) =
+  let f (name, ty, s) =
+    let to_string = Format.asprintf "%a" (Svg.pp_elt ()) in
     name, `Quick, fun () -> Alcotest.(check string) name (to_string ty) s
   in
   List.map f l
@@ -16,8 +15,26 @@ let svg_attributes = "svg attributes", tyxml_tests Svg.[
 
 ]
 
+let svg_filters = "svg filters", tyxml_tests Svg.[
+
+  "filter gaussian blur",
+  filter ~a:[ a_x (-0.1, None) ; a_y (-0.1, None) ; a_width (0.2, None) ; a_height (0.2, None) ]
+    [ feGaussianBlur ~a:[a_stdDeviation (0.2, None)] [] ],
+  "<filter x=\"-0.1\" y=\"-0.1\" width=\"0.2\" height=\"0.2\"><feGaussianBlur stdDeviation=\"0.2\"></feGaussianBlur></filter>" ;
+
+  "linear gradient",
+  linearGradient ~a:[ a_gradientTransform [`Rotate ((10., None), Some (0.5, 0.5))] ]
+    [
+      stop ~a:[ a_offset (`Percentage 0.) ; a_stop_color "white" ] [] ;
+      stop ~a:[ a_offset (`Percentage 100.) ; a_stop_color "red" ] []
+    ],
+  "<linearGradient gradientTransform=\"rotate(10 0.5 0.5)\"><stop offset=\"0%\" stop-color=\"white\"></stop><stop offset=\"100%\" stop-color=\"red\"></stop></linearGradient>"
+
+]
+
 let tests = [
   svg_attributes ;
+  svg_filters
 ]
 
 let () = Alcotest.run "tyxml-svg" tests
diff --git a/tyxml-syntax.opam b/tyxml-syntax.opam
index d556c36c6..5c04ead8b 100644
--- a/tyxml-syntax.opam
+++ b/tyxml-syntax.opam
@@ -9,7 +9,7 @@ doc: "https://ocsigen.org/tyxml/latest/manual/intro"
 bug-reports: "https://github.com/ocsigen/tyxml/issues"
 depends: [
   "dune" {>= "2.7"}
-  "ocaml" {>= "4.02"}
+  "ocaml" {>= "4.04"}
   "alcotest" {with-test}
   "ppxlib" {>= "0.18"}
   "re" {>= "1.5.0"}
diff --git a/tyxml.opam b/tyxml.opam
index 569701ece..d6384fd8f 100644
--- a/tyxml.opam
+++ b/tyxml.opam
@@ -11,7 +11,7 @@ doc: "https://ocsigen.org/tyxml/latest/manual/intro"
 bug-reports: "https://github.com/ocsigen/tyxml/issues"
 depends: [
   "dune" {>= "2.7"}
-  "ocaml" {>= "4.02"}
+  "ocaml" {>= "4.04"}
   "alcotest" {with-test}
   "re" {>= "1.5.0"}
   "seq"