diff --git a/jar.go b/jar.go
index 5ff2733..4ad290f 100644
--- a/jar.go
+++ b/jar.go
@@ -72,6 +72,15 @@ type Options struct {
 	// (useful for tests). If this is true, the value of Filename will be
 	// ignored.
 	NoPersist bool
+
+	// Filter specifies the filter to be used when deciding whether each cookie
+	// should be persisted to the filesystem.
+	Filter CookieFilter
+}
+
+// CookieFilter is a type for deciding whether a Cookie should be persisted
+type CookieFilter interface {
+	IsPersistent(*http.Cookie) bool
 }
 
 // Jar implements the http.CookieJar interface from the net/http package.
@@ -87,6 +96,9 @@ type Jar struct {
 	// entries is a set of entries, keyed by their eTLD+1 and subkeyed by
 	// their name/domain/path.
 	entries map[string]map[string]entry
+
+	// Filter from Options
+	filter CookieFilter
 }
 
 var noOptions Options
@@ -108,6 +120,11 @@ func newAtTime(o *Options, now time.Time) (*Jar, error) {
 	if o == nil {
 		o = &noOptions
 	}
+	jar.filter = DefaultFilter
+	if o.Filter != nil {
+		jar.filter = o.Filter
+	}
+
 	if jar.psList = o.PublicSuffixList; jar.psList == nil {
 		jar.psList = publicsuffix.List
 	}
@@ -144,10 +161,10 @@ type entry struct {
 	Path       string
 	Secure     bool
 	HttpOnly   bool
-	Persistent bool
 	HostOnly   bool
 	Expires    time.Time
 	Creation   time.Time
+	MaxAge     int
 	LastAccess time.Time
 
 	// Updated records when the cookie was updated.
@@ -203,6 +220,10 @@ func (e *entry) pathMatch(requestPath string) bool {
 	return false
 }
 
+func (e *entry) isExpiredAfter(t time.Time) bool {
+	return !e.Expires.IsZero() && t.After(e.Expires)
+}
+
 // hasDotSuffix reports whether s ends in "."+suffix.
 func hasDotSuffix(s, suffix string) bool {
 	return len(s) > len(suffix) && s[len(s)-len(suffix)-1] == '.' && s[len(s)-len(suffix):] == suffix
@@ -279,7 +300,7 @@ func (j *Jar) cookies(u *url.URL, now time.Time) (cookies []*http.Cookie) {
 
 	var selected []entry
 	for id, e := range submap {
-		if !e.Expires.After(now) {
+		if e.isExpiredAfter(now) {
 			// Save some space by deleting the value when the cookie
 			// expires. We can't delete the cookie itself because then
 			// we wouldn't know that the cookie had expired when
@@ -310,7 +331,7 @@ func (j *Jar) cookies(u *url.URL, now time.Time) (cookies []*http.Cookie) {
 // have Domain, Expires, HttpOnly, Name, Secure, Path, and Value filled
 // out. Expired cookies will not be returned. This function does not
 // modify the cookie jar.
-func (j *Jar) AllCookies() (cookies []*http.Cookie) {
+func (j *Jar) AllCookies() []*http.Cookie {
 	return j.allCookies(time.Now())
 }
 
@@ -321,7 +342,7 @@ func (j *Jar) allCookies(now time.Time) []*http.Cookie {
 	defer j.mu.Unlock()
 	for _, submap := range j.entries {
 		for _, e := range submap {
-			if !e.Expires.After(now) {
+			if e.isExpiredAfter(now) {
 				// Do not return expired cookies.
 				continue
 			}
@@ -393,7 +414,7 @@ var expiryRemovalDuration = 24 * time.Hour
 func (j *Jar) deleteExpired(now time.Time) {
 	for tld, submap := range j.entries {
 		for id, e := range submap {
-			if !e.Expires.After(now) && !e.Updated.Add(expiryRemovalDuration).After(now) {
+			if e.isExpiredAfter(now) && !e.Updated.Add(expiryRemovalDuration).After(now) {
 				delete(submap, id)
 			}
 		}
@@ -575,6 +596,27 @@ func defaultPath(path string) string {
 	return path[:i] // Path is either of form "/abc/xyz" or "/abc/xyz/".
 }
 
+// CookieFilterFunc implements CookieFilter by calling the underlying func
+type CookieFilterFunc func(*http.Cookie) bool
+
+// IsPersistent implements CookieFilter for arbitrary funcs
+func (cff CookieFilterFunc) IsPersistent(c *http.Cookie) bool {
+	return cff(c)
+}
+
+var (
+	// DefaultFilter is the previous behavior which does not persist session
+	// cookies.
+	DefaultFilter = CookieFilterFunc(func(c *http.Cookie) bool {
+		return c.MaxAge != 0 || !c.Expires.IsZero()
+	})
+
+	// AllowAllFilter does not check any cookie properties before persisting.
+	AllowAllFilter = CookieFilterFunc(func(_ *http.Cookie) bool {
+		return true
+	})
+)
+
 // newEntry creates an entry from a http.Cookie c. now is the current
 // time and is compared to c.Expires to determine deletion of c. defPath
 // and host are the default-path and the canonical host name of the URL
@@ -587,6 +629,7 @@ func defaultPath(path string) string {
 // A malformed c.Domain will result in an error.
 func (j *Jar) newEntry(c *http.Cookie, now time.Time, defPath, host string) (e entry, err error) {
 	e.Name = c.Name
+	e.MaxAge = c.MaxAge
 	if c.Path == "" || c.Path[0] != '/' {
 		e.Path = defPath
 	} else {
@@ -597,19 +640,16 @@ func (j *Jar) newEntry(c *http.Cookie, now time.Time, defPath, host string) (e e
 	if err != nil {
 		return e, err
 	}
+
 	// MaxAge takes precedence over Expires.
 	if c.MaxAge != 0 {
-		e.Persistent = true
 		e.Expires = now.Add(time.Duration(c.MaxAge) * time.Second)
 		if c.MaxAge < 0 {
 			return e, nil
 		}
-	} else if c.Expires.IsZero() {
-		e.Expires = endOfTime
 	} else {
-		e.Persistent = true
 		e.Expires = c.Expires
-		if !c.Expires.After(now) {
+		if e.isExpiredAfter(now) {
 			return e, nil
 		}
 	}
diff --git a/jar_test.go b/jar_test.go
index 5ea3467..49a066e 100644
--- a/jar_test.go
+++ b/jar_test.go
@@ -5,6 +5,7 @@
 package cookiejar
 
 import (
+	"encoding/json"
 	"fmt"
 	"io/ioutil"
 	"net/http"
@@ -1811,7 +1812,7 @@ func allCookies(jar *Jar, now time.Time) string {
 	var cs []string
 	for _, submap := range jar.entries {
 		for _, cookie := range submap {
-			if !cookie.Expires.After(now) {
+			if !cookie.Expires.IsZero() && now.After(cookie.Expires) {
 				continue
 			}
 			cs = append(cs, cookie.Name+"="+cookie.Value)
@@ -2067,6 +2068,74 @@ func TestRemoveAllHostIP(t *testing.T) {
 	testRemoveAllHost(t, mustParseURL("https://10.1.1.1"), "10.1.1.1", true)
 }
 
+func TestFilter(t *testing.T) {
+	j := newTestJar("")
+
+	google := mustParseURL("https://www.google.com")
+
+	j.SetCookies(
+		google,
+		[]*http.Cookie{
+			&http.Cookie{
+				Name:    "test-cookie",
+				Value:   "test-value",
+				Expires: time.Now().Add(24 * time.Hour),
+			},
+			&http.Cookie{
+				Name:  "test-cookie2",
+				Value: "test-value",
+			},
+		},
+	)
+
+	es, err := jsonRoundTrip(j)
+	if err != nil {
+		t.Fatalf("json failed: %v", err)
+	}
+
+	if len(es) != 1 {
+		t.Errorf("expected only one entry, got %d", len(es))
+	}
+
+	j.filter = CookieFilterFunc(func(_ *http.Cookie) bool {
+		return false
+	})
+
+	es, err = jsonRoundTrip(j)
+	if err != nil {
+		t.Fatalf("json failed: %v", err)
+	}
+
+	if len(es) > 0 {
+		t.Errorf("expected zero entries")
+	}
+
+	j.filter = AllowAllFilter
+
+	es, err = jsonRoundTrip(j)
+	if err != nil {
+		t.Fatalf("json failed: %v", err)
+	}
+
+	if len(es) < 2 {
+		t.Errorf("got fewer than two entries with AllowAllFilter")
+	}
+}
+
+func jsonRoundTrip(j *Jar) ([]entry, error) {
+	bs, err := j.MarshalJSON()
+	if err != nil {
+		return nil, err
+	}
+
+	var es []entry
+	if json.Unmarshal(bs, &es) != nil {
+		return nil, err
+	}
+
+	return es, nil
+}
+
 func testRemoveAllHost(t *testing.T, setURL *url.URL, removeHost string, shouldRemove bool) {
 	jar := newTestJar("")
 	google := mustParseURL("https://www.google.com")
diff --git a/serialize.go b/serialize.go
index 2792dfb..11507e8 100644
--- a/serialize.go
+++ b/serialize.go
@@ -8,6 +8,7 @@ import (
 	"encoding/json"
 	"io"
 	"log"
+	"net/http"
 	"os"
 	"path/filepath"
 	"sort"
@@ -137,7 +138,16 @@ func (j *Jar) allPersistentEntries() []entry {
 	var entries []entry
 	for _, submap := range j.entries {
 		for _, e := range submap {
-			if e.Persistent {
+			if j.filter.IsPersistent(&http.Cookie{
+				Domain:   e.Domain,
+				Expires:  e.Expires,
+				HttpOnly: e.HttpOnly,
+				MaxAge:   e.MaxAge,
+				Name:     e.Name,
+				Path:     e.Path,
+				Secure:   e.Secure,
+				Value:    e.Value,
+			}) {
 				entries = append(entries, e)
 			}
 		}