Convert short video clips into animated GIFs for Slack custom emoji and reactions. 128×128px, under 2MB, browser-only.
Slack custom emojis have tight constraints: the image must be under 2MB and Slack will automatically resize it to fit a 128×128 pixel square in the emoji picker. Upload something larger and Slack scales it down — which means you want to start close to that size to preserve detail. Animated GIFs are fully supported, and they loop in the emoji picker and in reactions, making them far more expressive than static images.
Slack also displays custom emojis in-line in messages at roughly 20–22px, so don't worry about fine detail at full resolution — bold shapes, high contrast, and a clear focal point matter far more than intricate linework.
The best Slack emojis are tight, square crops with high contrast and a punchy loop under 2 seconds. Think reaction faces, spinning logos, bouncing indicators, or a looping moment from a team video call. Because Slack downscales to 128×128, you'll want to pre-crop your clip to a square aspect ratio before converting — GifSmith's output will be letterboxed otherwise.
Frame rate isn't critical at emoji size — 10–15fps looks smooth while keeping the file well under the 2MB cap. Palette reduction to 64–128 colors is invisible at this display size and slashes the file significantly.
Select the Slack preset in GifSmith and the tool targets the dimensions and palette settings appropriate for custom emojis. Processing is entirely local in your browser via WebAssembly — nothing is uploaded to a server. The output GIF downloads instantly with no watermark, ready to upload straight to Slack under Workspace Settings → Customize → Add Custom Emoji.
For animated GIF reactions (the larger animated images sent in messages, not the emoji picker), use a higher duration setting and the Email preset to balance size and quality.
1. Find a short video clip with the moment you want (2 seconds or less works best).
2. Drop it onto the GifSmith forge.
3. Select the Slack preset button.
4. Trim to the exact frames using the start time slider.
5. Set Duration to 1–2 seconds.
6. Click STRIKE GIF and download.
7. In Slack: click your workspace name → Settings & Administration → Customize Slack → Add Custom Emoji, upload your GIF, and give it a name.