diff --git a/.env.production.sample b/.env.production.sample
index 4d058f0119180d..33fd457282a0d4 100644
--- a/.env.production.sample
+++ b/.env.production.sample
@@ -248,9 +248,12 @@ SMTP_FROM_ADDRESS=notifications@example.com
 # Various ways to customize Mastodon's behavior
 # ---------------
 
-# Maximum allowed character count
+# Maximum allowed character count in posts
 MAX_TOOT_CHARS=500
 
+# Maximum allowed character count in alt text
+MAX_ALT_TEXT_CHARS=1500
+
 # Maximum number of pinned posts
 MAX_PINNED_TOOTS=5
 
diff --git a/app/javascript/flavours/glitch/features/ui/components/focal_point_modal.jsx b/app/javascript/flavours/glitch/features/ui/components/focal_point_modal.jsx
index a5637d31cb6d8f..7f7ffd6ecf8f6b 100644
--- a/app/javascript/flavours/glitch/features/ui/components/focal_point_modal.jsx
+++ b/app/javascript/flavours/glitch/features/ui/components/focal_point_modal.jsx
@@ -22,6 +22,7 @@ import tesseractCorePath from 'tesseract.js-core/tesseract-core.wasm.js';
 // eslint-disable-next-line import/extensions
 import tesseractWorkerPath from 'tesseract.js/dist/worker.min.js';
 import { assetHost } from 'flavours/glitch/utils/config';
+import { maxAltTextChars } from 'flavours/glitch/initial_state';
 
 const messages = defineMessages({
   close: { id: 'lightbox.close', defaultMessage: 'Close' },
@@ -361,7 +362,7 @@ class FocalPointModal extends ImmutablePureComponent {
 
             <div className='setting-text__toolbar'>
               <button disabled={detecting || media.get('type') !== 'image' || is_changing_upload} className='link-button' onClick={this.handleTextDetection}><FormattedMessage id='upload_modal.detect_text' defaultMessage='Detect text from picture' /></button>
-              <CharacterCounter max={1500} text={detecting ? '' : description} />
+              <CharacterCounter max={maxAltTextChars} text={detecting ? '' : description} />
             </div>
 
             <Button disabled={!dirty || detecting || isUploadingThumbnail || length(description) > 1500 || is_changing_upload} text={intl.formatMessage(is_changing_upload ? messages.applying : messages.apply)} onClick={this.handleSubmit} />
diff --git a/app/javascript/flavours/glitch/initial_state.js b/app/javascript/flavours/glitch/initial_state.js
index 03be4ff6cfbf56..18875fcb51674e 100644
--- a/app/javascript/flavours/glitch/initial_state.js
+++ b/app/javascript/flavours/glitch/initial_state.js
@@ -145,6 +145,7 @@ export const statusPageUrl = getMeta('status_page_url');
 
 // Glitch-soc-specific settings
 export const maxChars = (initialState && initialState.max_toot_chars) || 500;
+export const maxAltTextChars = (initialState && initialState.max_alt_text_chars) || 1_500;
 export const favouriteModal = getMeta('favourite_modal');
 export const pollLimits = (initialState && initialState.poll_limits);
 export const defaultContentType = getMeta('default_content_type');
diff --git a/app/javascript/mastodon/features/ui/components/focal_point_modal.jsx b/app/javascript/mastodon/features/ui/components/focal_point_modal.jsx
index 11c4c523753fd9..fcceddbdb90127 100644
--- a/app/javascript/mastodon/features/ui/components/focal_point_modal.jsx
+++ b/app/javascript/mastodon/features/ui/components/focal_point_modal.jsx
@@ -23,6 +23,7 @@ import tesseractCorePath from 'tesseract.js-core/tesseract-core.wasm.js';
 // eslint-disable-next-line import/extensions
 import tesseractWorkerPath from 'tesseract.js/dist/worker.min.js';
 import { assetHost } from 'mastodon/utils/config';
+import { maxAltTextChars } from '../../../initial_state';
 
 const messages = defineMessages({
   close: { id: 'lightbox.close', defaultMessage: 'Close' },
@@ -369,7 +370,7 @@ class FocalPointModal extends ImmutablePureComponent {
               >
                 <FormattedMessage id='upload_modal.detect_text' defaultMessage='Detect text from picture' />
               </button>
-              <CharacterCounter max={1500} text={detecting ? '' : description} />
+              <CharacterCounter max={maxAltTextChars} text={detecting ? '' : description} />
             </div>
 
             <Button
diff --git a/app/javascript/mastodon/initial_state.js b/app/javascript/mastodon/initial_state.js
index cab7f1f6b217b8..884c8092048feb 100644
--- a/app/javascript/mastodon/initial_state.js
+++ b/app/javascript/mastodon/initial_state.js
@@ -136,5 +136,7 @@ export const statusPageUrl = getMeta('status_page_url');
 
 // Glitch-soc-specific settings
 export const maxChars = (initialState && initialState.max_toot_chars) || 500;
+export const maxAltTextChars = (initialState && initialState.max_alt_text_chars) || 1_500;
+
 
 export default initialState;
diff --git a/app/models/media_attachment.rb b/app/models/media_attachment.rb
index 62c9828c65d60c..859700ca14b2d7 100644
--- a/app/models/media_attachment.rb
+++ b/app/models/media_attachment.rb
@@ -37,7 +37,7 @@ class MediaAttachment < ApplicationRecord
   enum type: { :image => 0, :gifv => 1, :video => 2, :unknown => 3, :audio => 4 }
   enum processing: { :queued => 0, :in_progress => 1, :complete => 2, :failed => 3 }, _prefix: true
 
-  MAX_DESCRIPTION_LENGTH = 1_500
+  MAX_DESCRIPTION_LENGTH = (ENV['MAX_ALT_TEXT_CHARS'] || 1_500).to_i
 
   IMAGE_LIMIT = (ENV['MAX_IMAGE_SIZE'] || 10.megabytes).to_i
   VIDEO_LIMIT = (ENV['MAX_VIDEO_SIZE'] || 40.megabytes).to_i
@@ -199,7 +199,7 @@ class MediaAttachment < ApplicationRecord
   remotable_attachment :thumbnail, IMAGE_LIMIT, suppress_errors: true, download_on_assign: false
 
   validates :account, presence: true
-  validates :description, length: { maximum: MAX_DESCRIPTION_LENGTH }
+  validates :description, length: { maximum: MAX_DESCRIPTION_LENGTH }, if: :local?
   validates :file, presence: true, if: :local?
   validates :thumbnail, absence: true, if: -> { local? && !audio_or_video? }
 
diff --git a/app/serializers/initial_state_serializer.rb b/app/serializers/initial_state_serializer.rb
index 45ee06e12c733e..4c4d922f0520c7 100644
--- a/app/serializers/initial_state_serializer.rb
+++ b/app/serializers/initial_state_serializer.rb
@@ -6,7 +6,7 @@ class InitialStateSerializer < ActiveModel::Serializer
   attributes :meta, :compose, :accounts,
              :media_attachments, :settings,
              :max_toot_chars, :poll_limits,
-             :languages
+             :languages, :max_alt_text_chars
 
   has_one :push_subscription, serializer: REST::WebPushSubscriptionSerializer
   has_one :role, serializer: REST::RoleSerializer
@@ -15,6 +15,10 @@ def max_toot_chars
     StatusLengthValidator::MAX_CHARS
   end
 
+  def max_alt_text_chars
+    MediaAttachment::MAX_DESCRIPTION_LENGTH
+  end
+
   def poll_limits
     {
       max_options: PollValidator::MAX_OPTIONS,
diff --git a/app/serializers/rest/instance_serializer.rb b/app/serializers/rest/instance_serializer.rb
index 41adaed80dbda3..66e1551526d593 100644
--- a/app/serializers/rest/instance_serializer.rb
+++ b/app/serializers/rest/instance_serializer.rb
@@ -66,6 +66,7 @@ def configuration
         video_size_limit: MediaAttachment::VIDEO_LIMIT,
         video_frame_rate_limit: MediaAttachment::MAX_VIDEO_FRAME_RATE,
         video_matrix_limit: MediaAttachment::MAX_VIDEO_MATRIX_LIMIT,
+        max_alt_text_characters: MediaAttachment::MAX_DESCRIPTION_LENGTH
       },
 
       polls: {
diff --git a/app/serializers/rest/v1/instance_serializer.rb b/app/serializers/rest/v1/instance_serializer.rb
index 0c2101404678de..e59e5e4162898c 100644
--- a/app/serializers/rest/v1/instance_serializer.rb
+++ b/app/serializers/rest/v1/instance_serializer.rb
@@ -4,7 +4,7 @@ class REST::V1::InstanceSerializer < ActiveModel::Serializer
   include RoutingHelper
 
   attributes :uri, :title, :short_description, :description, :email,
-             :version, :urls, :stats, :thumbnail, :max_toot_chars, :poll_limits,
+             :version, :urls, :stats, :thumbnail, :max_toot_chars, :max_alt_text_chars, :poll_limits,
              :languages, :registrations, :approval_required, :invites_enabled,
              :configuration
 
@@ -40,6 +40,10 @@ def max_toot_chars
     StatusLengthValidator::MAX_CHARS
   end
 
+  def max_alt_text_chars
+    MediaAttachment::MAX_DESCRIPTION_LENGTH
+  end
+
   def poll_limits
     {
       max_options: PollValidator::MAX_OPTIONS,
@@ -89,6 +93,7 @@ def configuration
         video_size_limit: MediaAttachment::VIDEO_LIMIT,
         video_frame_rate_limit: MediaAttachment::MAX_VIDEO_FRAME_RATE,
         video_matrix_limit: MediaAttachment::MAX_VIDEO_MATRIX_LIMIT,
+        max_alt_text_characters: MediaAttachment::MAX_DESCRIPTION_LENGTH
       },
 
       polls: {