Convert WEBM to APNG Online

Convert WebM to APNG Online

A WebM is a video file; an APNG is a single image file that animates. Converting one to the other gives you a looping clip that drops straight into a README, a wiki, a chat window or an <img> tag — no player, no autoplay policy, no codec negotiation. The trade is weight: every APNG frame is stored losslessly, so a few seconds of video becomes a file measured in hundreds of kilobytes. Files upload over an encrypted connection, are processed on our servers, and are deleted automatically after a few hours — no sign-up, no watermark.

How to Convert WebM to APNG

1. Upload Your WebM File: Drag and drop the .webm onto the page or click to browse. This page accepts .webm input; queue several and each one converts to its own APNG.
2. Set the Framerate: The Framerate dropdown opens on 10 FPS (Recommended) and runs from 1 FPS (Slideshow) up to 50 FPS (Max Speed). Real-time length is held — the source is resampled to the rate you pick and every frame is stamped with an exact 1/N-second delay, so 10 FPS on a two-second clip yields 20 frames that still play for two seconds.
3. Set the Image Resolution: Keep original is preselected. Switch to Resolution Percentage, a Preset Resolution (16P up to 4320p — these are height presets, so the width follows the source aspect), or an explicit Width × Height. Resolution is the biggest single lever on output size, because APNG cost scales with pixels multiplied by frames.
4. Convert and Download: Click Convert and save the .apng. The animation is written with an infinite loop count and then run through a Zopfli recompression pass before you download it.

What the Conversion Actually Produces

Transparency: What Happens to an Alpha WebM

WebM can carry transparency, but it does not store alpha inside the VP8/VP9 picture. It codes a second, separate alpha plane and attaches it to each video block, and the container flags this with an AlphaMode marker. The decoder used in this conversion reads the picture and not that side channel, so a WebM with a transparent background arrives fully opaque, and everything that used to be see-through lands as solid black in the APNG. This is worth knowing before you convert a logo sting or a sticker exported from a motion tool.

Two reliable ways around it:

• Export the animation from your editor as a numbered PNG sequence and build the animation from those frames with PNG to APNG — PNG alpha survives the whole chain intact.
• If your source tool can write ProRes 4444, a MOV carries its alpha through the same pipeline correctly; MOV to APNG takes that path.

APNG vs GIF vs Animated WebP

Frequently Asked Questions

Why is my APNG so much bigger than the WebM it came from?

Because they are not doing the same job. VP9 in a WebM predicts each frame from the ones around it and throws away detail you are unlikely to notice; APNG stores each frame with lossless compression and no cross-frame prediction beyond simple region diffs. A 2-second 480×270 clip that occupied about 12 KB as VP9 came out around 110 KB as an APNG in our before/after check — roughly nine times larger. Shrink it by lowering the Framerate, cutting the Image Resolution, or trimming the clip with the WebM cutter before converting.

Does the transparent background in my WebM survive?

No. The alpha channel a WebM carries alongside VP8/VP9 is not read by the decoder in this pipeline, so transparent pixels arrive opaque and render black. If transparency is the reason you are converting, export a PNG sequence from your source tool instead and assemble it with PNG to APNG.

What framerate should I choose?

10 FPS (Recommended) is the preselected value and is the right starting point for UI captures, screen recordings and short loops. Go to 15–20 FPS for fast camera motion, and drop to 5–8 FPS for slow pans where you want the file small. Because APNG has no lossy inter-frame compression, frame count translates almost directly into bytes — halving the framerate roughly halves the file.

Will the APNG play at the wrong speed if I change the framerate?

No. Frames are resampled at the rate you pick and the per-frame delay is written as an exact 1/N-second fraction, so the output duration matches the source. This is one of APNG's genuine advantages over GIF: GIF stores delays in whole centiseconds, so rates like 15 FPS (6.67 cs) cannot be expressed exactly and drift slightly.

Does the APNG keep the audio from my WebM?

No. APNG is an image format with no audio track at all, so the WebM's audio stream is discarded. If you need a portable clip that keeps sound, convert WebM to MP4 instead.

What happens in software that does not understand APNG?

It shows the still image stored in the file's ordinary PNG data instead of animating. The W3C PNG Third Edition Recommendation (24 June 2025) makes this explicit: a non-animated decoder ignores the APNG-specific chunks and displays the static image. That graceful degradation is the main practical reason to prefer APNG over animated WebP, which renders nothing at all where it is unsupported.

How long a WebM can I sensibly convert?

Keep it to a few seconds. Output size scales with resolution multiplied by frame count, so a 30-second 1080p clip at 20 FPS becomes an enormous file long before it becomes a useful one. For anything longer than a short loop, keep it as video — MP4 will be a fraction of the size for the same footage.

Should I use APNG or GIF for this clip?

Choose APNG when the clip has gradients, photographic content or soft anti-aliased edges that a 256-colour palette would band or dither. Choose GIF when maximum reach matters — older email clients and legacy tooling handle GIF and may not handle APNG — and accept the palette limit; WebM to GIF does that conversion. Built from the same 20 extracted frames, the GIF came out at roughly 60% of the APNG's size in our check, which is what the drop to 256 colours buys you.