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Browser only - 100% private

Slack Emoji Maker - 128x128 PNG under 128 KB

Resize any image to Slack's exact custom emoji spec: 128 x 128 PNG, under 128 KB, with transparency preserved. Browser-only, no upload, no signup.

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Upload an image to build a Slack emoji.

128 x 128 PNG with transparency, target file size 128 KB

Slack Emoji online with ImgShifter

Slack Emoji Maker - 128x128 PNG under 128 KB sizes any image to 128 x 128 (1:1) PNG with transparency preserved - the exact spec the platform requires. Non-square sources are scaled to fit and padded with transparent pixels on the shorter axis so your subject keeps its original aspect ratio and nothing gets cropped off. If you'd rather crop to a tight square first (zoom into a face, for example), use the Crop Image tool with 1:1 ratio before running it through this maker.

Slack's 128 KB file size cap is tighter than Discord's 256 KB, so the same design has to compress harder. PNGs of simple emoji artwork at 128 x 128 are comfortably under 50 KB; photographic content typically lands at 60-100 KB. The tool warns if the result exceeds the cap, and you can always compress further with the dedicated 100 KB compressor.

Everything runs in your browser. The resize and PNG export happen on your device using the Canvas API. iPhone HEIC files are decoded locally with a WebAssembly module before sizing. No upload, no signup, no watermark.

Related tools

Other ImgShifter tools people use alongside Slack Emoji.

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Discord Emoji

Resize any image to Discord's exact 128 x 128 PNG emoji spec with transparency preserved and the 256 KB upload cap respected. Browser-only, no upload.

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Telegram Sticker

Resize any image to Telegram's exact 512 x 512 PNG sticker spec with transparency preserved. One side is exactly 512 px per Telegram's rule, with transparent padding on the shorter axis.

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Image to Favicon

Turn any image into a complete favicon set in your browser. ICO, PNG, Apple touch icon, Android Chrome icons, manifest, and an HTML snippet - bundled as a ZIP.

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Compress

Reduce image file size with a quality slider and instant before/after stats. Powered by jsquash MozJPEG, libwebp, and AVIF encoders.

Frequently asked questions

Short answers for image workflows, privacy, and supported formats.