Google's rules, in plain numbers
Google publishes hard requirements for animated image ads on the Display Network, and the review process enforces them without sentiment. The rules for GIFs:
- Animated GIF is an accepted format. Video has its own ad products; for image slots, GIF is the motion option.
- 150 KB maximum file size. Not a guideline, a rejection threshold.
- 30 seconds of animation, tops. Looping is allowed, but the animation has to stop by the 30 second mark.
- Slower than 5 fps. Anything at 5 fps or above fails review, so 4 fps is the highest safe setting.
- Standard slot sizes. The workhorses are 300x250 (medium rectangle), 728x90 (leaderboard), 160x600 (wide skyscraper), and 320x50 (mobile banner).
Platforms edit specs quietly, so confirm against Google's current documentation before a big flight. But the shape of the problem is stable: everything on that list is easy to satisfy except the file size, which is where display creative goes to be humbled.
What 150 KB actually buys
Be honest with yourself early: 150 KB is brutal. A casual GIF for Slack can run twenty times that. At display sizes with a real message on it, the budget forces design decisions, and the ones that work are all subtractions.
- Few frames. At 4 fps, a 3 second creative is 12 frames. Think of it as a slideshow with intent: logo, claim, offer, CTA, each held.
- Flat colors. Photography and gradients are palette hogs. Solid brand colors compress to almost nothing.
- 64 colors or fewer. Most flat creative survives 64 untouched, and plenty survives 32.
- Hard cuts, not fades. A crossfade rewrites every pixel of every in-between frame, and GIF charges for every changed pixel. A cut changes one frame and costs pocket change.
- Hold still where you can. GIF stores what changes between frames. A card held for a second is nearly free; wall-to-wall motion is the expensive kind.
None of this makes the ad worse. Display runs on glances, and a message that reads in two beats was always going to beat one that needs ten. The format is just enforcing it.
The settings that hit the numbers
The converter's controls map onto Google's list directly. The frame rate slider goes down to 3 fps, comfortably under the 5 fps ceiling. The width and height fields take exact pixel values, so a 300x250 comes out at 300x250, not a near miss that gets bounced. And the estimated file size recalculates live with every adjustment, which turns 150 KB from a surprise at upload time into a number you watch while you work.
When the estimate is stubbornly over, the Extra Compression dial typically takes another 30 to 50% off, and the palette is the next biggest lever after that. The general small-file playbook is in the small GIF recipe, and if you're starting from a finished GIF that needs to make weight, the compression guide covers that path.
Design for the frame it stops on
The 30 second rule has a quiet consequence: your ad will spend most of its life as a still. A 6 second creative that loops a few times inside the window still stops, and whatever frame it stops on is the ad from then on. So build the ending to stand alone: the final card carries the offer, the brand, and the CTA with no context required, and the beauty shots live in the middle. Email people learn the mirror image of this lesson from classic Outlook freezing frame one; the email guide has that version. Here, the last frame does the selling.
Client creative never leaves the building
Everything here runs client-side: the file loads in your browser, the encode happens on your machine, and the download appears without the creative ever touching a third-party server. For agency work that matters more than convenience. An embargoed campaign shouldn't be sitting in some converter's upload bucket a month before launch. There's also no signup and no watermark, and the page keeps working offline once loaded, so the pitch-day workflow doesn't depend on conference wifi. Drag the master video, or an overweight existing GIF, into the tool and start subtracting.