How is this different from the GIF Edge Refiner and GIF Edge Feather?

This tool never blurs or blends anything: it only reclassifies alpha values that are already close to 0 or 255, snapping them the rest of the way. The Edge Refiner blends color and alpha over a neighborhood to smooth jaggies, and the Edge Feather deliberately creates a new gradient fade; this tool does neither.

What counts as a 'stray' pixel?

Any pixel whose alpha falls below the low threshold (default 32) or above the high threshold (default 223), and (unless edge radius is set to 0) sits near a hard 0/255 alpha boundary. Genuine mid-range alpha, like an intentional soft shadow or feathered edge, is left completely alone.

Why would a GIF have stray fringe pixels in the first place?

They commonly come from lossy re-encoding, sloppy background removal, or resizing operations that introduce a thin ring of nearly-but-not-quite transparent or opaque pixels around the intended hard edge.

Can I clean the whole frame instead of just near edges?

Yes, set the edge search radius to 0 and every matching pixel across the whole frame will be snapped, regardless of proximity to a hard boundary.

GIF Edge Cleaner - Remove Stray Fringe Pixels from an Animated GIF

Overview

Introduction

This tool cleans up stray semi-transparent fringe pixels near an animated GIF's alpha edges, entirely client-side, without blurring or blending anything.

It's a targeted cleanup step: near-0 alpha snaps down to fully transparent, near-255 alpha snaps up to fully opaque, and everything genuinely in between is left untouched.

What Is GIF Edge Cleaner?

A client-side GIF alpha-cleanup tool that, for every frame, reclassifies pixels whose alpha is below a low threshold or above a high threshold (and, by default, that also sit within a small radius of a hard 0/255 boundary), snapping them the rest of the way to fully transparent or fully opaque.

Setting the edge search radius to 0 applies the same threshold snapping across the whole frame rather than only near hard boundaries.

How GIF Edge Cleaner Works

For each pixel, its alpha is compared against `lowThreshold` and `highThreshold`. A pixel below the low threshold (but not already 0) or above the high threshold (but not already 255) is flagged as a stray candidate.

If `edgeRadius` is greater than 0, a flagged pixel is only actually snapped if a genuinely fully-transparent or fully-opaque pixel is found within that radius (confirming it's really fringe near a hard edge, not an intentional mid-range gradient); with `edgeRadius` set to 0, every flagged pixel is snapped unconditionally.

When To Use GIF Edge Cleaner

Use it on a GIF that shows a faint halo or ring of slightly-transparent pixels around an otherwise hard-edged subject, often left over from a lossy export or an earlier background-removal pass.

It's also a good final cleanup step after using the GIF Background Remover or GIF Chroma Key Remover, since color-distance-based keying can leave a thin ring of partial transparency at the boundary.

Often used alongside GIF Edge Refiner, GIF Edge Feather and GIF Background Remover.

Features

Advantages

Never blurs or blends color, unlike the GIF Edge Refiner: only alpha values are reclassified.
Leaves genuine mid-range alpha (intentional soft edges or feathers) completely untouched.
Runs entirely client-side; the uploaded animation is never sent to a server.

Limitations

Won't fix a genuinely soft or intentionally feathered edge: by design, it only targets near-0/near-255 stray values, not real mid-range alpha.
Choosing thresholds too close to 128 can start snapping pixels that were meant to stay semi-transparent.

Examples

Clean up a chroma-key halo

Input

A 160x160 animated GIF with a faint semi-transparent green-tinted ring left after background removal, low threshold 32, high threshold 223, edge radius 3

Output

A 160x160 animated GIF with the faint ring snapped to fully transparent, leaving a clean hard edge

The stray near-0-alpha ring pixels near the hard silhouette boundary are cleared; the subject's fully opaque interior is untouched.

Best Practices & Notes

Best Practices

Run this after a background-removal or chroma-key pass, since those operations are the most common source of stray fringe pixels.
Keep the default thresholds (32 and 223) unless you have a specific reason to be more or less aggressive.
Use edge radius 0 only if you're confident there's no intentional mid-range alpha anywhere in the frame, since it applies globally.

Developer Notes

cleanGifEdgeFringe in gif-edge-cleaner.ts maps either cleanFrameFringe (global, unconditional threshold snap, used when edgeRadius is 0) or cleanFrameEdgeFringe (the same snap but gated on proximity to a genuinely hard 0/255 neighbor) across every frame of a DecodedGif. Unlike gif-edge-refiner.ts and gif-edge-feather.ts, this file never touches RGB values or performs any weighted averaging: it's a pure per-pixel alpha reclassification.

GIF Edge Cleaner Use Cases

Cleaning up a faint semi-transparent halo left after chroma-key or color-distance background removal
Removing lossy-re-encoding fringe artifacts around a GIF's silhouette
Tightening up alpha values before re-encoding a GIF through another lossy tool

Common Mistakes

Setting the low/high thresholds too close to 128, accidentally snapping genuinely intentional mid-range alpha.
Using edge radius 0 on a frame that has an intentional feathered or soft-shadow region, flattening it unintentionally.

Tips

Run the GIF Background Remover or GIF Chroma Key Remover first, then this tool as a follow-up cleanup pass.
If you want an intentional soft edge instead of a clean hard one, use the GIF Edge Feather tool instead of tightening thresholds here.

GIF Edge Cleaner