diff --git a/.github/workflows/pullpreview.yml b/.github/workflows/pullpreview.yml
index bd2e163..2c4bbdb 100644
--- a/.github/workflows/pullpreview.yml
+++ b/.github/workflows/pullpreview.yml
@@ -32,6 +32,7 @@ jobs:
           instance_type: micro
           # only required if using custom domain for your preview environments
           dns: custom.pullpreview.com
+          max_domain_length: 30
           # only required if fetching images from private registry
           registries: docker://${{ secrets.GHCR_PAT }}@ghcr.io
           # how long this instance will stay alive (each further commit will reset the timer)
diff --git a/action.yml b/action.yml
index 8c80a5b..302a0f9 100644
--- a/action.yml
+++ b/action.yml
@@ -15,6 +15,9 @@ inputs:
   dns:
     description: "Which DNS suffix to use"
     default: "my.pullpreview.com"
+  max_domain_length:
+    description: "Maximum length of fully qualified domain name. Note that it cannot be greater than 62 characters due to LetsEncrypt restrictions."
+    default: "62"
   label:
     description: "Label to use for triggering preview deployments"
     default: "pullpreview"
@@ -120,3 +123,4 @@ runs:
     GITHUB_TOKEN: "${{ inputs.github_token }}"
     PULLPREVIEW_LICENSE: "${{ inputs.license }}"
     PULLPREVIEW_PROVIDER: "${{ inputs.provider }}"
+    PULLPREVIEW_MAX_DOMAIN_LENGTH: "${{ inputs.max_domain_length }}"
diff --git a/lib/pull_preview/instance.rb b/lib/pull_preview/instance.rb
index ee870a9..975bdce 100644
--- a/lib/pull_preview/instance.rb
+++ b/lib/pull_preview/instance.rb
@@ -3,6 +3,9 @@
 
 module PullPreview
   class Instance
+    # https://community.letsencrypt.org/t/a-certificate-for-a-63-character-domain/78870/4
+    DEFAULT_MAX_DOMAIN_LENGTH = 62
+
     include Utils
 
     attr_reader :admins
@@ -79,14 +82,24 @@ def public_ip
       access_details.ip_address
     end
 
+    def max_domain_length
+      value = ENV.fetch("PULLPREVIEW_MAX_DOMAIN_LENGTH", DEFAULT_MAX_DOMAIN_LENGTH).to_i
+      value = DEFAULT_MAX_DOMAIN_LENGTH if value <= 0 || value > DEFAULT_MAX_DOMAIN_LENGTH
+      value
+    end
+
+    # Leave 8 chars for an additional subdomain that could be needed by the deployed app.
+    # Disabled if custom domain length is specified.
+    def reserved_space_for_user_subdomain
+      max_domain_length != DEFAULT_MAX_DOMAIN_LENGTH ? 0 : 8
+    end
+
     def public_dns
-      reserved_space_for_user_subdomain = 8
-      # https://community.letsencrypt.org/t/a-certificate-for-a-63-character-domain/78870/4
-      remaining_chars_for_subdomain = 62 - reserved_space_for_user_subdomain - dns.size - public_ip.size - "ip".size - ("." * 3).size
+      remaining_chars_for_subdomain = max_domain_length - reserved_space_for_user_subdomain - dns.size - public_ip.size - "ip".size - ("." * 3).size
       [
-        [subdomain[0..remaining_chars_for_subdomain], "ip", public_ip.gsub(".", "-")].join("-").squeeze("-"),
+        [subdomain[0..[(remaining_chars_for_subdomain - 1), 0].max], "ip", public_ip.gsub(".", "-")].join("-").squeeze("-"),
         dns
-      ].join(".")
+      ].reject{|part| part.empty?}.join(".")
     end
 
     def url