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GIF Resizer

Resize an animated GIF proportionally in your browser while keeping its visible frames and per-frame timing local.

Privacy: your files never leave your device. All processing happens locally in your browser.

How to use

  1. 1.Choose an animated GIF up to 20 MB and confirm the detected source canvas.
  2. 2.Enter the target width in whole pixels; the matching height is calculated automatically.
  3. 3.Select Resize GIF, then download and review the new animation at its intended display size.

About GIF Resizer

GIF Resizer changes the pixel dimensions of an animated GIF without sending the file to a server. Choose one GIF, enter the output width in whole pixels, and the page calculates the matching height from the original canvas ratio. It decodes the animation in the current browser tab, renders each visible frame at the requested size, builds a new GIF, and provides one download link. The source file, decoded pixels, and resulting Blob stay on the device unless you choose to download the result.

A GIF is not always a series of complete pictures. Many animations store a first image plus smaller patches that update only part of the logical canvas. A patch can also carry a disposal instruction that says whether the next frame should keep the prior pixels, clear the changed rectangle, or restore an earlier canvas. Resizing each raw patch independently can leave missing backgrounds, incorrect trails, or transparent holes. This tool first composites every frame according to those instructions, then resizes the complete visible canvas. The output therefore represents what a viewer should see at each frame boundary rather than exposing implementation patches.

Width is the only geometry control because it keeps the ratio unambiguous. If a source canvas is 800 by 600 and you enter 400, the output is 400 by 300. The tool rounds the calculated height to a whole pixel. It does not crop, pad, stretch one axis independently, rotate the animation, change the frame order, add captions, or choose a new aspect ratio. Use an image cropper or a dedicated GIF editor before resizing when those changes are intended.

The browser protects itself with explicit bounds. The selected file may be up to 20 MB. Its logical canvas may be no more than 4,096 pixels on either side and three million pixels in one frame. The animation may contain up to 50 image frames, with limits for compressed patches and the combined output work. Those checks matter because a small compressed GIF can expand into many canvas pixels. A file that exceeds a bound is rejected before a large output canvas is allocated, rather than producing a partial download or freezing the page.

The export is a fresh GIF encoding, not a byte-for-byte resize of the original stream. GIF uses palette-based color, so the browser creates a palette of up to 256 colors for each full output frame. Visible frame order and decoded delays are retained, but original palette tables, metadata extensions, optimization strategy, and a finite loop count are not copied. The resulting GIF repeats continuously. Transparent GIF pixels remain one-bit transparent, which is the transparency model supported by GIF itself. Gradients, dithering, and fine photographic detail can look different after a second palette conversion; inspect the downloaded animation before publishing it.

Resizing down usually reduces the number of pixels, but it does not guarantee a smaller file. Frame content, palette choices, and GIF compression affect the final byte count. The page reports the actual output dimensions, number of frames, and final size so that a changed result is visible. It does not promise a percentage reduction, silently overwrite the source, or upload the result to an optimization service.

For a dependable workflow, start with a copy of the original GIF, select it, confirm the source canvas shown by the page, enter the width required by the destination, and download the resized version. Open the result in the browser or target application and watch the first cycle for timing, text legibility, and edge quality. Test a representative animation at the intended display size, especially when it has small text, transparency, rapid motion, or gradients. The tool does not edit video, preserve audio, convert to MP4 or WebP, guarantee social-network compatibility, or infer the best width for a particular website.

Canvas rendering and local download behavior can vary slightly between browsers, displays, and color-management settings. This page uses standard browser canvas drawing and Blob download APIs, so it is best suited to normal web GIFs that the current browser can decode. If a source has unsupported or damaged frame data, misleading dimensions, too much decoded work, or an invalid GIF signature, the page shows an error and leaves no stale download in place. No account is needed and nothing is stored after the current tab is closed.

Methodology & sources

Read and bound the GIF header and frame descriptors, decode local frames, composite patches according to disposal behavior, scale each complete visible canvas proportionally, quantize each output frame to at most 256 GIF colors, retain decoded delays, and export a new local GIF Blob.

Frequently asked questions

Does resizing upload my GIF?
No. GIF decoding, canvas rendering, palette encoding, and the download Blob run in the current browser tab.
Will the height stay proportional?
Yes. The page calculates a whole-pixel height from the source canvas ratio and the width you enter.
Does it preserve every GIF setting?
It preserves the decoded visible frames and frame delays, but creates a new palette-based GIF and does not retain original metadata, palette tables, or a finite loop count.
Will the resized GIF always be smaller?
No. Fewer pixels often help, but animation content, palette selection, and GIF compression can still make a result larger.

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