The GIF Toolbox handles four small jobs around animated images: “Combine images”, “Split frames”, “Add text” and “Change speed”. Combine first normalises the pictures to the aspect ratio of the first one on a browser canvas, then hands them to ffmpeg for a two-pass palette GIF; Split decodes a GIF/APNG/animated WebP into a set of PNGs; Add text divides the animation into frames at a uniform frame rate first, draws the text frame by frame with the browser's system fonts and composites it back; Change speed recalculates the frame timings.

These are not the same kind of processing: Combine takes at most 60 images and widths of only 320/480/640px; Add text has a 300-frame ceiling; Change speed covers 0.25x–4x and automatically caps the result at 50 fps when the speed-up would go above it. The ffmpeg paths run on single-threaded ffmpeg.wasm inside the browser.

1. 01Choose a sub-tool— switch to “Combine images”, “Split frames”, “Add text” or “Change speed” depending on the job.
2. 02Prepare the material— for Combine pick at least 2 images and put them in order; the other three need a GIF, APNG or animated WebP selected.
3. 03Set the parameters— Combine takes 0.1–2 seconds per frame, a width and a background; Add text takes a top or bottom position, a font size, a colour and a black outline; Change speed takes 0.25x–4x.
4. 04Run and download— Combine, Split and Change speed submit an ffmpeg job directly; Add text automatically chains two jobs, “split frames → draw text on canvas → recompose”.

How many can be combined

— 60 frames at most; an animation used as a source only contributes its first frame, and all images are normalised to the first image's aspect ratio.

Split frames carries no timing

— the exported PNGs are numbered in decode order, but the original animation's variable frame delays are not preserved, and the download is packed as a zip.

Ceiling for adding text

— 40 characters of text at most, top or bottom only; if the estimated or actual frame count exceeds 300 the job is refused, and the frame rate is clamped to 5–30 fps for the text workflow.

Speed range

— 0.25x–4x; GIF frame delays are treated as at least 0.02 seconds and a speed-up lands at roughly 50 fps at most.

What it does not do

— no frame-by-frame drawing timeline, no free-position subtitle track and no GIF optimiser; to make a GIF from a video use Video to GIF.

Images and animations are processed locally in the browser by canvas and ffmpeg.wasm and are not uploaded; the first call to an ffmpeg path downloads about 31–32 MB of single-threaded core from the site's asset domain or jsDelivr.