diff --git a/.env.production.sample b/.env.production.sample
index 91fcce6ac45..27de27de493 100644
--- a/.env.production.sample
+++ b/.env.production.sample
@@ -134,3 +134,6 @@ STREAMING_CLUSTER_NUM=1
 # If you use Docker, you may want to assign UID/GID manually.
 # UID=1000
 # GID=1000
+
+# Maximum allowed character count
+# MAX_TOOT_CHARS=500
diff --git a/app/javascript/mastodon/features/compose/components/compose_form.js b/app/javascript/mastodon/features/compose/components/compose_form.js
index 13a41f23f87..aaca4549329 100644
--- a/app/javascript/mastodon/features/compose/components/compose_form.js
+++ b/app/javascript/mastodon/features/compose/components/compose_form.js
@@ -19,6 +19,9 @@ import ImmutablePureComponent from 'react-immutable-pure-component';
 import { length } from 'stringz';
 import { countableText } from '../util/counter';
 import ComposeAttachOptions from '../../../../glitch/components/compose/attach_options/index';
+import initialState from '../../../initial_state';
+
+const maxChars = initialState.max_toot_chars;
 
 const messages = defineMessages({
   placeholder: { id: 'compose_form.placeholder', defaultMessage: 'What is on your mind?' },
@@ -205,7 +208,7 @@ export default class ComposeForm extends ImmutablePureComponent {
       }
     }
 
-    const submitDisabled = disabled || this.props.is_uploading || length(text) > 500 || (text.length !== 0 && text.trim().length === 0);
+    const submitDisabled = disabled || this.props.is_uploading || length(text) > maxChars || (text.length !== 0 && text.trim().length === 0);
 
     return (
       <div className='compose-form'>
@@ -255,7 +258,7 @@ export default class ComposeForm extends ImmutablePureComponent {
         </div>
 
         <div className='compose-form__publish'>
-          <div className='character-counter__wrapper'><CharacterCounter max={500} text={text} /></div>
+          <div className='character-counter__wrapper'><CharacterCounter max={maxChars} text={text} /></div>
           <div className='compose-form__publish-button-wrapper'>
             {
               showSideArm ?
diff --git a/app/serializers/initial_state_serializer.rb b/app/serializers/initial_state_serializer.rb
index 787c5add33c..9dfa019f59d 100644
--- a/app/serializers/initial_state_serializer.rb
+++ b/app/serializers/initial_state_serializer.rb
@@ -2,10 +2,15 @@
 
 class InitialStateSerializer < ActiveModel::Serializer
   attributes :meta, :compose, :accounts,
-             :media_attachments, :settings, :push_subscription
+             :media_attachments, :settings, :push_subscription,
+             :max_toot_chars
 
   has_many :custom_emojis, serializer: REST::CustomEmojiSerializer
 
+  def max_toot_chars
+    StatusLengthValidator::MAX_CHARS
+  end
+
   def custom_emojis
     CustomEmoji.local.where(disabled: false)
   end
diff --git a/app/serializers/rest/instance_serializer.rb b/app/serializers/rest/instance_serializer.rb
index 2898011fd8a..abbacc37476 100644
--- a/app/serializers/rest/instance_serializer.rb
+++ b/app/serializers/rest/instance_serializer.rb
@@ -4,7 +4,7 @@ class REST::InstanceSerializer < ActiveModel::Serializer
   include RoutingHelper
 
   attributes :uri, :title, :description, :email,
-             :version, :urls, :stats, :thumbnail
+             :version, :urls, :stats, :thumbnail, :max_toot_chars
 
   def uri
     Rails.configuration.x.local_domain
@@ -30,6 +30,10 @@ class REST::InstanceSerializer < ActiveModel::Serializer
     full_asset_url(instance_presenter.thumbnail.file.url) if instance_presenter.thumbnail
   end
 
+  def max_toot_chars
+    StatusLengthValidator::MAX_CHARS
+  end
+
   def stats
     {
       user_count: instance_presenter.user_count,
diff --git a/app/validators/status_length_validator.rb b/app/validators/status_length_validator.rb
index 2ce5d1ee999..79d17742a90 100644
--- a/app/validators/status_length_validator.rb
+++ b/app/validators/status_length_validator.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 class StatusLengthValidator < ActiveModel::Validator
-  MAX_CHARS = 512
+  MAX_CHARS = (ENV['MAX_TOOT_CHARS'] || 500).to_i
 
   def validate(status)
     return unless status.local? && !status.reblog?