diff --git a/PrivaPub.Tests/Http/MediaLifecycleTests.cs b/PrivaPub.Tests/Http/MediaLifecycleTests.cs
index c049d83..c2dbc9b 100644
--- a/PrivaPub.Tests/Http/MediaLifecycleTests.cs
+++ b/PrivaPub.Tests/Http/MediaLifecycleTests.cs
@@ -74,6 +74,38 @@ namespace PrivaPub.Tests.Http
 			Assert.Equal("edited out", (await DB.Default.Find<MediaAttachment>().OneAsync(dropped, Token)).TrashReason);
 		}
 
+		// a posted picture's description and focus change by editing its post (media_attributes), not by PUT, as on Mastodon
+		[Fact]
+		public async Task An_edit_describes_its_media_again_and_keeps_what_it_is_not_sent()
+		{
+			var alice = await _host.Mastodon("alice");
+			var id = await Upload(alice, "a.jpg");
+			var status = (await alice.Client.Post("/api/v1/statuses", ("status", "described later"), ("media_ids[]", id),
+				("spoiler_text", "a warning"), ("sensitive", "true"), ("language", "it"))).Ok();
+			var statusId = status.Body.Text("id");
+			Assert.Equal(HttpStatusCode.NotFound, (await alice.Client.Put($"/api/v1/media/{id}", ("description", "too late"))).Status);
+
+			var edited = (await alice.Client.Json(HttpMethod.Put, $"/api/v1/statuses/{statusId}", new System.Text.Json.Nodes.JsonObject
+			{
+				["status"] = "described now",
+				["spoiler_text"] = "a warning",
+				["sensitive"] = true,
+				["media_ids"] = new System.Text.Json.Nodes.JsonArray(id),
+				["media_attributes"] = new System.Text.Json.Nodes.JsonArray(new System.Text.Json.Nodes.JsonObject { ["id"] = id, ["description"] = "a red square", ["focus"] = "0.5,0.5" })
+			})).Ok();
+
+			Assert.Equal("a red square", edited.Body["media_attachments"]![0]!.Text("description"));
+			Assert.Equal(0.5, edited.Body["media_attachments"]![0]!["meta"]!["focus"]!["x"]!.GetValue<double>());
+			Assert.Equal("a warning", edited.Body.Text("spoiler_text"));
+			Assert.True(edited.Body["sensitive"]!.GetValue<bool>());
+			Assert.Equal("it", edited.Body.Text("language"));
+			Assert.Equal("a red square", (await DB.Default.Find<MediaAttachment>().OneAsync(id, Token)).Description);
+
+			// an edit that doesn't send media keeps them, described as they were
+			var kept = (await alice.Client.Put($"/api/v1/statuses/{statusId}", ("status", "media kept"))).Ok();
+			Assert.Equal("a red square", kept.Body["media_attachments"]![0]!.Text("description"));
+		}
+
 		[Fact]
 		public async Task A_replaced_avatar_is_trashed_and_a_picture_that_is_not_one_is_refused()
 		{
diff --git a/PrivaPub/Api/Mastodon/Controllers/MediaController.cs b/PrivaPub/Api/Mastodon/Controllers/MediaController.cs
index f7108ef..5d09ac9 100644
--- a/PrivaPub/Api/Mastodon/Controllers/MediaController.cs
+++ b/PrivaPub/Api/Mastodon/Controllers/MediaController.cs
@@ -64,10 +64,11 @@ namespace PrivaPub.Api.Mastodon.Controllers
 			};
 		}
 
+		// as on Mastodon, only media not posted yet: a posted one's description and focus change by editing its post (media_attributes)
 		[HttpPut("/api/v1/media/{id}"), Scope("write:media")]
 		public async Task<IActionResult> Update(string id, CancellationToken token)
 		{
-			var attachment = await DB.Default.Find<MediaAttachment>().Match(m => m.ID == id && m.OwnerAvatarId == MyId && m.TrashedAt == null && m.ProfileOfAvatarId == null).ExecuteFirstAsync(token);
+			var attachment = await DB.Default.Find<MediaAttachment>().Match(m => m.ID == id && m.OwnerAvatarId == MyId && m.TrashedAt == null && m.ProfileOfAvatarId == null && m.PostId == null).ExecuteFirstAsync(token);
 			if (attachment == default)
 				return NotFoundError();
 			if (Params.Has("description"))
diff --git a/PrivaPub/Api/Mastodon/Controllers/StatusesController.cs b/PrivaPub/Api/Mastodon/Controllers/StatusesController.cs
index 72f34b9..729e1c0 100644
--- a/PrivaPub/Api/Mastodon/Controllers/StatusesController.cs
+++ b/PrivaPub/Api/Mastodon/Controllers/StatusesController.cs
@@ -167,11 +167,41 @@ namespace PrivaPub.Api.Mastodon.Controllers
 				SpoilerText = Params.Get("spoiler_text"),
 				Sensitive = Params.Bool("sensitive") ?? false,
 				Language = Params.Get("language"),
-				MediaIds = Params.Has("media_ids") ? Params.List("media_ids") : default
+				MediaIds = Params.Has("media_ids") ? Params.List("media_ids") : default,
+				MediaChanges = MediaAttributes()
 			}, token);
 			return outcome.Ok ? Json(await _mapper.Status(outcome.Post, MyId, token)) : Error(outcome.Status, outcome.Error);
 		}
 
+		// Mastodon's media_attributes: a JSON body's array of objects, or a form's media_attributes[i][field] or
+		// media_attributes[][field] (each field then listed in the same order)
+		IReadOnlyList<MediaChange> MediaAttributes()
+		{
+			var changes = new List<MediaChange>();
+			if (Params.Json is { ValueKind: System.Text.Json.JsonValueKind.Object } json && json.TryGetProperty("media_attributes", out var array)
+				&& array.ValueKind == System.Text.Json.JsonValueKind.Array)
+			{
+				foreach (var item in array.EnumerateArray().Where(i => i.ValueKind == System.Text.Json.JsonValueKind.Object).Take(4))
+				{
+					var hasDescription = item.TryGetProperty("description", out var description);
+					changes.Add(new MediaChange(Text(item, "id"), hasDescription, hasDescription ? Text(item, "description") : default, Text(item, "focus")));
+				}
+				return changes;
+			}
+			for (var i = 0; i < 4 && Params.Get($"media_attributes[{i}][id]") is { } id; i++)
+				changes.Add(new MediaChange(id, Params.Has($"media_attributes[{i}][description]"), Params.Get($"media_attributes[{i}][description]"), Params.Get($"media_attributes[{i}][focus]")));
+			var ids = Params.List("media_attributes[][id]");
+			var descriptions = Params.List("media_attributes[][description]");
+			var foci = Params.List("media_attributes[][focus]");
+			for (var i = 0; i < Math.Min(ids.Count, 4); i++)
+				changes.Add(new MediaChange(ids[i], i < descriptions.Count, i < descriptions.Count ? descriptions[i] : default, i < foci.Count ? foci[i] : default));
+			return changes;
+
+			static string Text(System.Text.Json.JsonElement item, string name) => item.TryGetProperty(name, out var value)
+				? value.ValueKind == System.Text.Json.JsonValueKind.String ? value.GetString() : value.ValueKind is System.Text.Json.JsonValueKind.Null ? default : value.GetRawText()
+				: default;
+		}
+
 		[HttpDelete("/api/v1/statuses/{id}"), Scope("write:statuses")]
 		public async Task<IActionResult> Delete(string id, CancellationToken token)
 		{
diff --git a/PrivaPub/Domain/Statuses/StatusService.cs b/PrivaPub/Domain/Statuses/StatusService.cs
index 09a06d9..4306c47 100644
--- a/PrivaPub/Domain/Statuses/StatusService.cs
+++ b/PrivaPub/Domain/Statuses/StatusService.cs
@@ -24,6 +24,9 @@ using PostEntity = PrivaPub.Models.Post.Post;
 
 namespace PrivaPub.Domain.Statuses
 {
+	// an attachment's description or focal point changed by an edit (Mastodon's media_attributes)
+	public sealed record MediaChange(string Id, bool HasDescription, string Description, string Focus);
+
 	public sealed class StatusDraft
 	{
 		public string Text { get; init; }
@@ -38,6 +41,7 @@ namespace PrivaPub.Domain.Statuses
 		public string ConversationId { get; init; }
 		public IReadOnlyList<string> Recipients { get; init; } = Array.Empty<string>();
 		public IReadOnlyList<string> MediaIds { get; init; }
+		public IReadOnlyList<MediaChange> MediaChanges { get; init; } = Array.Empty<MediaChange>();
 		// the scheduled post being published, whose media are reserved for it alone
 		public string ScheduledStatusId { get; init; }
 		public double? Latitude { get; init; }
@@ -320,6 +324,23 @@ namespace PrivaPub.Domain.Statuses
 
 			var plain = draft.PlainText || post.ContentFormat == ContentFormat.Plain;
 			var rendered = plain ? await _content.PlainText(draft.Text ?? string.Empty, token) : await _content.Markdown(draft.Text ?? string.Empty, token);
+			// descriptions and focal points changed by the edit, on the media it keeps or those the post already has
+			var described = media ?? (draft.MediaChanges.Count > 0
+				? await DB.Default.Find<MediaAttachment>().Match(m => m.PostId == post.ID && m.TrashedAt == null).ExecuteAsync(token)
+				: default);
+			foreach (var change in draft.MediaChanges)
+			{
+				if (described?.FirstOrDefault(m => m.ID == change.Id) is not { } attachment)
+					continue;
+				if (change.HasDescription)
+					attachment.Description = string.IsNullOrWhiteSpace(change.Description) ? default : change.Description.Trim()[..Math.Min(change.Description.Trim().Length, 1500)];
+				if (Domain.Media.FocalPoint.Parse(change.Focus) is { } focus)
+					attachment.Focus = focus;
+				await DB.Default.Update<MediaAttachment>().MatchID(attachment.ID)
+					.Modify(m => m.Description, attachment.Description).Modify(m => m.Focus, attachment.Focus).ExecuteAsync(token);
+			}
+			if (media == default && described != default)
+				post.Media = post.Media.Select(copy => described.FirstOrDefault(m => m.ID == copy.AttachmentId) is { } changed ? ToPostMedia(changed) : copy).ToList();
 			if (media != default)
 			{
 				if (!await Claim(media, post.ID, default, token))
@@ -330,6 +351,7 @@ namespace PrivaPub.Domain.Statuses
 				await _media.Trash(m => m.PostId == post.ID && !kept.Contains(m.ID), "edited out", token);
 			}
 			post.Title = draft.Title == default ? post.Title : Clean(draft.Title);
+			// as on Mastodon, an edit sends the whole post: no warning sent is no warning (the language alone falls back)
 			post.SpoilerText = Clean(draft.SpoilerText);
 			post.HasContentWarning = draft.Sensitive || post.SpoilerText != default;
 			post.Text = draft.Text;