Convexy

Convert an MP4 to an animated GIF on iPhone

Yes, the GIF will probably be larger than the MP4 you started with. That is not a mistake — it is arithmetic, and once you understand it you can keep the file under control.

Why the GIF is bigger than the video

This is the question everyone asks, and the answer is genuinely interesting.

H.264 (inside your MP4) is a video codec. It looks at a frame, compares it to the previous one, and mostly stores only what changed. A static background costs almost nothing. It uses motion estimation, frequency-domain transforms and thirty years of research to squeeze a moving picture into a few kilobytes per second.

GIF is an image format from 1987. Each frame is an 8-bit palettised image, compressed with LZW — a general-purpose scheme designed for flat-coloured logos and line art. It has some inter-frame tricks, but nothing remotely comparable. Fundamentally, you are storing a stack of images.

So converting MP4 to GIF means throwing away decades of compression research and paying for it in bytes. A 3 MB MP4 becoming a 12 MB GIF is not a bug. It is the format doing exactly what it does.

The arithmetic you can actually control

GIF size scales with frames × pixels per frame. There is no bitrate dial to hide behind, which means the two settings that matter are blunt and effective:

Worked through: a 10-second clip at 20 fps and 960 px is 200 frames of roughly 960×540 pixels. The same clip at 10 fps and 480 px is 100 frames of roughly 480×270 — one eighth of the data before compression even starts. Same clip, same duration, dramatically different file.

The Loop setting (infinite, once, or three times) has no effect on size at all. It just tells the player what to do at the end.

Convexy uses the first 15 seconds only. This is a hard cap, not an option. Longer GIFs at any usable frame rate produce files that most chat apps, forums and issue trackers will simply reject. If the moment you want is later in the video, trim it in the Photos app first and convert the trimmed copy.

What GIF costs you besides bytes

Two things, both permanent:

Colour. Every frame is reduced to a 256-colour palette. Your MP4 has millions. Flat graphics, text and screen recordings survive this easily — they were what the palette was designed for. Photographic footage does not: expect banding in skies and gradients, and a dithered texture across skin tones that was not in the original.

Sound. GIF has no audio track and never has. If anyone is speaking in your clip, the GIF silences them. There is no setting for this because there is nothing to set.

When to do it anyway

GIF earns its keep in exactly one situation: the destination will not play video inline. A GIF autoplays, loops, and needs no player, no click and no permission — in chat apps, forums, wikis, bug trackers, READMEs and email clients that have not changed since 2009.

That makes it right for a short UI demo in a ticket, a bug reproduction, a silent reaction clip, or a small looping animation on a page. It makes it wrong for anything with speech, anything long, anything colourful, and anything going somewhere that could simply embed the MP4.

If the place you are sending it can play video — and most now can — send the MP4. Smaller, sharper, longer, with sound. The GIF is a workaround, and it is worth being honest that you are working around something.

How to do it

  1. Bring the MP4 into Convexy

    Tap Browse files to pick it from Files, choose it from Photos, or share it into Convexy from another app.

  2. Choose animated GIF

    Convexy lists only what the file can actually become — GIF sits alongside MOV, M4V, extracted audio and still frames.

  3. Drop the width first

    Max width is the strongest size control you have, because it scales quadratically. Try 480 px, or even 320.

  4. Then drop the frame rate

    10 fps halves the frames against 20 fps and looks fine for most footage. Only raise it if the motion visibly judders.

  5. Convert, then save or share

    Only the first 15 seconds are used. Everything runs on your device — save the GIF to Files or Photos, or share it on.

Common questions

Why is my GIF larger than the MP4?

Because MP4 uses a modern video codec that mostly stores what changed between frames, and GIF stores a stack of 8-bit images compressed with a scheme from the 1980s. You are trading away thirty years of compression research. A GIF several times the size of its source MP4 is entirely normal.

How do I make the GIF smaller?

Reduce the max width first — it scales quadratically, so halving the width cuts each frame to a quarter of its pixels. Then drop the frame rate to 10 fps, which halves the number of frames against 20 fps. Then shorten the clip. Those three, in that order, are the whole toolkit — GIF has no quality slider.

Can I make a GIF longer than 15 seconds?

No. Convexy caps GIF output at the first 15 seconds of the video, and it is a hard limit rather than a setting. Beyond that the files become large enough that most places you would want to post them will reject them anyway. Trim the source clip in the Photos app first if you need a later section.

Will the GIF have sound?

No. The GIF format has no audio track — there is physically nowhere to store it. If the audio matters, either send the MP4 instead or extract the audio to M4A as a separate file.

Why does my GIF look worse than the video?

The 256-colour palette. Every frame is reduced to 8-bit colour, which photographic footage cannot survive cleanly — you get banding in gradients and dithering on skin tones. Screen recordings, text and flat graphics come through far better, because that is the kind of image GIF was designed for.

Is there a better option than GIF?

Almost always: the MP4 you already have. It is smaller, sharper, unlimited in length and has sound. GIF's only real advantage is that it autoplays and loops inline anywhere with no player — so use it when the destination cannot embed video, and not otherwise.