X Giffer

pronounced "jiffer"

Get X Giffer for Firefox (desktop and Android) · Open the Android share app

Save GIFs from X (Twitter) as real .gif files. X stores "GIFs" as silent MP4s (video.twimg.com/tweet_video/<id>.mp4). This project fetches that MP4 and converts it to an animated GIF on your own device: it decodes the video frame by frame onto a canvas, using the browser's own decoder, and encodes the frames with gifenc. No third-party conversion service is involved. Short videos (up to 60 seconds) can be turned into GIFs the same way, and any video can be saved as an MP4.

It has two parts that share extension/converter.js:

Part	What it does
extension/	Firefox extension. Adds GIF and MP4 buttons to every GIF and video on x.com.
pwa/	Small web app for Android. Share an X post to it and it gives you back the GIF. Short videos work too.

Firefox extension

Install: get it from Firefox Add-ons at https://addons.mozilla.org/en-US/firefox/addon/x-giffer/. It works in Firefox on desktop and in Firefox for Android (version 142 or newer).

From source (temporary install): open about:debugging#/runtime/this-firefox, choose Load Temporary Add-on… and pick extension/manifest.json. The add-on stays loaded until you restart Firefox.

Your own signed build: release Firefox only installs signed add-ons. If you've modified it, you can sign your own copy as an unlisted add-on (free, automatic, and not published). First change browser_specific_settings.gecko.id in extension/manifest.json to an ID of your own, because the published add-on's ID is taken:

npx web-ext sign -s extension --channel unlisted \
  --api-key "$AMO_JWT_ISSUER" --api-secret "$AMO_JWT_SECRET"

Get the keys at https://addons.mozilla.org/developers/addon/api/key/, then open the .xpi it writes to web-ext-artifacts/ in Firefox. Alternatively, set xpinstall.signatures.required to false in Developer Edition, Nightly or ESR.

Using it: hover a GIF or video on X and the GIF / MP4 buttons appear in its top-right corner. The GIF button shows conversion progress, and the file lands in your Downloads folder as <user>_<postid>.gif. For videos, MP4 saves the best quality X has, and GIF works for videos up to 60 seconds long (hover the ✗ to see why one failed). A GIF made from a video is also kept to about 200 million pixels in total (width × height × frames). That's roughly 1100 px wide for a 10-second clip, or 440 px for a minute, whatever the preset says. Real footage barely compresses as a GIF: a 9-second 1080p clip at full size comes to over 200 MB.

Quality presets

Pick one in the add-on's Preferences, or in the dropdown in the PWA:

Preset	Size	Frame rate	Colours
Original (default)	source size	every source frame, exact timing	256
Balanced	up to 720 px wide	up to 30 fps	256
Small	up to 480 px wide	up to 20 fps	256
Tiny	up to 320 px wide	up to 12 fps	128

The converter reads the frame timestamps from the MP4, so it keeps the source's own frames and durations instead of resampling. It also merges identical consecutive frames. GIFs can't play faster than 50 fps, so higher frame rates are thinned to fit.

Colours come from a single palette built from samples of every frame, so gradients don't band differently from frame to frame. Pixels that haven't changed are left transparent so the previous frame shows through, and so are pixels that differ only by compression noise. Static areas stay steady, and files come out about 30% smaller.

Android share shortcut (PWA)

It's hosted at https://nyaadesu.github.io/x-giffer/, deployed from main by .github/workflows/pages.yml. A fork can host its own copy by setting Settings → Pages → Source to GitHub Actions.

1. On your phone, open https://nyaadesu.github.io/x-giffer/ in Chrome and choose ⋮ → Add to Home screen → Install.
2. In the X app, open a post with a GIF or a short video and tap Share → X Giffer. The app opens, converts the GIF with your chosen quality preset, and saves it to Downloads. Share GIF (to send it straight to another app) and Save GIF are there too.

You can also paste a post link into the app directly. Pasted links are never saved automatically.

Settings in the app (remembered on the device):

• Quality is used for every conversion, including shared posts.
• Save automatically when shared is on by default. Turn it off to pick Share or Save yourself.
• Then close the app closes the window once the GIF is saved, so a share drops you back in the X app. The app still has to open while it converts: Android always opens a share target's window, and a web app can't convert or save files in the background. A post with several GIFs keeps the app open: Chrome asks before a site saves multiple files at once (allow it once and it remembers), and closing would dismiss that prompt.

Notes:

• Android only offers installed PWAs in the share sheet, and Firefox for Android doesn't support Web Share Targets. You need Chrome, or a Chromium-based browser such as Edge, Brave or Samsung Internet, to install the PWA. Once installed, the shortcut works from any app.
• The app looks up the post with the public FxTwitter API (api.fxtwitter.com), because X's own API needs authentication. The MP4 is then downloaded directly from X's CDN.

How it works / gotchas

• video.twimg.com returns 403 for any Referer that isn't X's, so every MP4 fetch uses referrerPolicy: "no-referrer".
• In the extension, the conversion runs in the background page (Firefox background pages have a DOM), so it isn't affected by x.com's CSP and doesn't slow down the tab.
• Firefox on macOS can't decode a <video> in a background page at all (it fails with "Expected Planar YCbCr image", or just never loads). So frames are decoded with WebCodecs (VideoDecoder), reading the H.264 samples straight out of the MP4 (extension/mp4.js). A <video> that seeks to each frame is the fallback where WebCodecs is missing (Firefox for Android) or fails. Don't make the <video> the main path again without testing on a Mac.
• Real X videos are streamed through MSE (blob: URLs), so the page never shows their MP4 URL. The extension reads the media ID from the video's poster and looks the post up on X's own embed API (cdn.syndication.twimg.com, the endpoint embedded posts use) to find the MP4 versions X keeps. For a GIF it picks the smallest one that is at least as wide as the quality preset, so less has to be downloaded. Posts that X won't embed (age-restricted or private) can't be fetched this way.

License

MIT, see LICENSE. Bundles gifenc 1.0.3 (MIT), unmodified.

Not affiliated with X Corp.