Cannot add caption to images on mobile

[vincepettit]

On the mobile view of the admin section you cannot add ally text, captions, or descriptions to media uploads

[sabernhardt]

Hi and welcome to Trac!

Could you add screenshots and/or specific instructions for how you tried to add these details?

I don't know if something is not loading properly for you, or if the interface for editing those details is simply too hard to find on mobile.

[vincepettit]

No options on mobile view (Safari - iPhone 13 Pro)

[vincepettit]

Replying to sabernhardt:

Hi and welcome to Trac!

Could you add screenshots and/or specific instructions for how you tried to add these details?

I don't know if something is not loading properly for you, or if the interface for editing those details is simply too hard to find on mobile.

When adding / editing a post in mobile I go to the feature image section. Upload or choose an image but there is nowhere to add captions. The only way that it is possible is you upload in the media area outside of the post.

It seems that the CSS is hiding that part of the screen that is available on desktop.

[sabernhardt]

Thanks for clarification. That panel apparently remains hidden at certain sizes because selecting an image does not add the visible class.

@media only screen and (max-width: 640px), screen and (max-height: 400px) {
	.media-sidebar {
		bottom: 120%;
	}
	.media-sidebar.visible {
		bottom: 0;
	}
}

[vincepettit]

Any news on this update? It’s frustrating not being able to edit the captions when adding images.

On mobile viewports (max-width 640px or max-height 400px), the media modal's .media-sidebar is positioned off-screen by the responsive CSS rule in media-views.css:

.media-sidebar { bottom: 120%; }
.media-sidebar.visible { bottom: 0; }

The .visible class is added in AttachmentsBrowser#createSingle() only when the current state's id is 'insert' (the "Insert into post" flow). Every other state that lets the user select a single attachment — featured image picker, replace image, gallery flows — leaves the sidebar parked off-screen, making the Alternative Text, Caption, and Description fields unreachable on narrow viewports.

This is the root cause behind the long-standing report in Trac #55200 ("Cannot add caption to images on mobile"), where comment 3 already identified the exact CSS but no patch was filed. The most user-visible impact is that authors setting a featured image from a mobile browser cannot add alt text or a caption without leaving the post editor and going to the Media Library.

This PR extends the allowlist in createSingle() to include the other selection flows that surface attachment metadata in the sidebar:

• featured-image (Set featured image)
• replace-image (Replace media inside Image Details)
• gallery-edit (Edit Gallery)
• gallery-library (Add to Gallery)

The dispose side already removes the class unconditionally, so the show/hide pairing stays balanced.

## Testing

1. Open a post in the block editor on a viewport narrower than 640px (or use device emulation in DevTools).
2. In the post sidebar, click Set featured image.
3. Select an image from the Media Library.
4. Before this patch: the right-hand "Attachment Details" panel (with Alternative Text, Caption, etc.) is positioned off-screen and unreachable.
5. After this patch: the panel slides on-screen as it does in the "Insert into post" flow.

The same fix takes effect in the Replace Media flow and Gallery editing flows.

## Use of AI Tools

AI assistance: Yes
Tool(s): Claude Code
Model(s): Claude Opus 4.7
Used for:

• Locating the responsible code path (browser.js:761) and the CSS rule that hides the sidebar off-screen.
• Searching Trac for prior reports, which surfaced #55200 and confirmed that comment 3 from sabernhardt had already diagnosed the root cause four years ago.

The bug was found by a human (encountered while trying to set alt text on a featured image from a mobile browser). Diagnosis used AI assistance to trace the responsible code and locate the existing Trac ticket. The fix itself is a small, targeted code change reviewed and tested manually by a human before submission.

I just tried testing in Playground, and I can see that the modal for selecting the featured image shows the properties. But it's not seeming to show anything when the modal is open for another image, like for the Image block:

​https://github.com/user-attachments/assets/40c6c1d2-97f5-4f3d-a6b6-ab1354fb0930

[adrianduffell]

This was discussed in today’s bug scrub. As we are deep in the 7.1 beta, I'll punt this.

Adding early to flag it for possible inclusion in 7.2.

[pedrofigueroa1989]

I have suggested a small change in the PR to include core blocks, too:
​https://github.com/WordPress/wordpress-develop/pull/11864#discussion_r3643818474