A reaction GIF is a joke, and a joke is timing. Land one frame late and the punchline limps in. Land it on the frame and the whole channel feels it. The trouble is that most GIF makers treat trim as a polite suggestion, you drag a fuzzy slider, hope for the best, and ship three extra seconds of dead air before the good part. So here is the better way: clip the perfect moment for team chat, then shrink it small enough that Slack and Discord show it playing inline instead of folding it into a sad little file card nobody opens.
Why timing is the whole game
The best reaction GIFs run one to three seconds. Long enough to read, short enough to loop forever without wearing out its welcome. The catch is that the moment you actually want, the eyebrow raise, the slow head turn, the exact instant someone realizes they posted that in the company-wide channel, usually lives between two frames a normal slider will never let you land on.
That is the entire reason to use What the GIF. The timeline shows seconds and frames, and the trim handles snap to frame boundaries instead of floating somewhere in the neighborhood. Set your in-point, then nudge it with the arrow keys one frame at a time until the GIF opens on the exact beat. A reaction that starts half a beat early reads as a glitch; one that starts on the frame reads as comedy. Same logic at the tail, cut the out-point the instant the expression peaks, before the subject blinks or the camera drifts, so the loop snaps back clean. If you want the full method, the frame-perfect trimming guide walks through it.
Crop for where it'll actually be seen
Half your team reads Slack on a phone, in a thread, with a keyboard covering the bottom third of the screen. A wide 16:9 clip shrinks to a postage stamp in that space and the joke dies in the letterboxing. Crop with intent instead, and lock it to a real ratio so nothing squashes:
- 1:1 (square), the safe default for reactions. Reads well on desktop and mobile alike, fills the inline preview, wastes no space. When in doubt, this.
- 9:16 (vertical), best when the action is a person or a phone screen. It dominates a mobile thread and feels native to how people actually hold the device.
- 4:5, the gentle middle ground when a square crops off too much of the action but full vertical is overkill.
- 4:3 or 16:9, keep the wider frames only when the joke genuinely needs the room (a UI demo, two people in frame). Just know they'll read smaller on mobile.
Because the crop in the converter locks to these exact ratios, your output is never squashed or stretched, a 1:1 crop is a true square, not a slightly-off rectangle that gives everyone's face an uncanny wideness. Drag the crop box over the part of the frame that carries the joke and let the rest go.
Get the file small enough to preview inline
Both platforms quietly punish big files, just differently. Discord shows GIFs inline and autoplays them, but free accounts cap uploads around 10 MB (Nitro and boosted servers go higher). Slack will post almost anything, yet only animates smaller GIFs directly in the message, go too big and it collapses into a click-to-open attachment, which, again, nobody clicks. Aim to keep reaction GIFs in the 2–5 MB range. Under 2 MB is the comfortable zone where it just appears and plays.
Two settings do almost all the work:
- Frame rate: 10–15 fps. GIFs are not film. Most reactions look great at 12 fps, and the file shrinks dramatically versus 24 or 30. Use the low end for slow moments, a deadpan stare doesn't need 30 frames a second, and the high end only when there's genuinely fast motion to preserve.
- Fewer colors. A GIF tops out at 256 colors. Drop it to 64 or 128 and most clips look identical while the file gets meaningfully lighter. Flat, graphic content. UI, cartoons, text, screen recordings, survives aggressive color cuts beautifully. Gradients, sunsets, and skin tones want a little more headroom, so nudge back up if you see banding.
Shorter also means smaller, every frame you trim is bytes you never ship. This is where frame-perfect trimming pays off twice: a tighter clip is both funnier and lighter. Cutting a 4-second clip to 2 seconds roughly halves the file before you touch any other setting.
The full workflow, start to drop
- Load your clip. Drag a video, or a screen recording, into What the GIF. Everything runs in the browser tab, so your raw footage never leaves your machine (more on why that matters in a second).
- Trim to the punchline. Set your in and out points on the frame timeline, then arrow-key your way to the exact frames where the GIF should open and close. Keep the whole thing inside the 1–3 second range.
- Crop for the channel. Lock the crop to 1:1 for a universal reaction, or 9:16 if your audience lives on mobile. Position the box over the part of the frame doing the comedic heavy lifting.
- Shrink it. Set fps to 10–15 and drop the color count to 64–128. Watch the estimated size and keep it under ~2–5 MB.
- Export and drop it in. Save the GIF, then drag it straight into the Slack or Discord message box. In Discord it autoplays inline; in Slack a small GIF animates in-thread. Done. Read the room, hit send.
Clip from your own screen recordings, locally
The reaction GIFs that actually kill are usually the inside jokes: a bug doing something genuinely absurd, a teammate's hot take from a recorded standup, the loading spinner that has personally wronged you. Those come from screen recordings, and screen recordings are exactly the footage you don't want sitting on some random conversion server you've never heard of.
What the GIF runs the entire conversion client-side. Nothing uploads, there's no signup wall, and there's no watermark stamped across your punchline. You can clip a moment out of an internal demo, turn it into a GIF, and post it to the channel without that footage ever touching a third party, which also makes it the rare GIF tool your IT and security folks won't develop strong feelings about. If your clips are heading somewhere more official than #random, the bug reports and demos guide covers the higher-stakes version, where the same screen-recording-to-GIF move documents a repro instead of landing a joke.
Quick etiquette and size cheat sheet
- One to three seconds. If it needs longer to make sense, it's a video, not a reaction.
- Square by default, vertical for people. When in doubt, 1:1.
- Under ~2 MB feels instant. Under ~5 MB is fine. Bigger than that and Slack tucks it behind a click.
- 12 fps, 64–128 colors is a reliable starting recipe for almost any clip.
- Read the room. A GIF reply is punctuation, not a paragraph. One great one beats five mediocre ones, and timing beats volume every time.
The free tool is ad-supported, which is a very small toll for never uploading your footage and never wearing a watermark. Get the timing right and the channel does the rest.
