Check if Image is WebP Online Free Tool
Check if Image is WebP by reading RIFF/WEBP magic bytes. Detects lossy, lossless, animated, alpha, Exif, ICCP, XMP flags. Free, client-side.
Drop a file in and get a byte-level verdict: WebP or not, lossy vs lossless, animation, alpha, and the VP8X flag bits for ICCP / EXIF / XMP.
Click to upload or drag and drop
Any file — the tool reads the first 32 KB locally, regardless of extension
Details
First 16 bytes (hex)
A WebP always starts with the RIFF container — 52 49 46 46 then the 4-byte size, then 57 45 42 50 ("WEBP").
How to Use Check if Image is WebP Online Free Tool
- Drop any file onto the upload area. The extension is ignored - the tool reads the first 32 KB locally.
- Read the verdict: green means WebP with variant (VP8 lossy, VP8L lossless, or VP8X extended) plus animation/alpha hints; amber means not a WebP.
- Inspect the details card: dimensions for all three variants, lossy vs lossless vs extended, the VP8X flag byte broken out into Alpha / Animation / ICCP / Exif / XMP rows.
- Check the hex line: the first 16 bytes in uppercase hex. A real WebP starts with
52 49 46 46(RIFF), four size bytes, then57 45 42 50(WEBP). - Note the frame count: for animated WebP (VP8X with animation flag), the tool counts ANMF chunks visible in the first 32 KB, which covers most typical files.
- Press
Ctrl+Enter(⌘+Enteron Mac) to re-run the check on the last file after a re-save. - Copy a plain-text report or Download a timestamped `.txt` that embeds the original filename for archiving.
Frequently asked questions
Is my file uploaded anywhere?
No. The check runs entirely in your browser via File.slice().arrayBuffer(). Only the first 32 KB is read – never the whole file – and nothing touches the network.
How does the tool detect WebP format?
It verifies the RIFF container: bytes 0-3 must be RIFF, and bytes 8-11 must be WEBP. The first chunk code (at bytes 12-15) then picks the variant: VP8, VP8L, or VP8X.
What’s the difference between VP8, VP8L, and VP8X?
VP8 is the lossy compressor (similar to MPEG-4 I-frames). VP8L is lossless. VP8X is the “extended” container chunk that enables animation, alpha, and metadata – it must be first if the file uses any of those features.
Does it detect animated WebP?
Yes. An animated WebP always has VP8X first, with the animation flag bit set, followed by an ANIM chunk and one or more ANMF frame chunks. The tool reads the VP8X flag byte and counts ANMF chunks in the first 32 KB.
Why does the tool say “in first 32 KB”?
To stay fast and memory-light, the tool slices just the first 32 KB of the file. For most WebP files that is enough to cover the variant chunk, the VP8X flags, and the first several ANMF frames. Very long animations may report a lower frame count than the full file has.
Does file extension matter?
No. The check reads the actual magic bytes, so a WebP renamed to photo.jpg is still identified correctly, and a fake .webp is flagged as not WebP.
What are the ICCP / Exif / XMP rows?
Bits in the VP8X flag byte advertise optional metadata chunks: ICCP for an ICC colour profile, Exif for camera metadata, XMP for Adobe’s extended metadata schema. The tool also scans subsequent chunks in case the bits were not set but the chunks exist.
Does it read WebP dimensions?
Yes – all three variants store dimensions in slightly different places. VP8 reads them from the key frame header, VP8L from a 14-bit packed field after the signature, and VP8X from the 3-byte canvas size fields.
Is there a file size limit?
No. Only the first 32 KB is read regardless of total file size.
Does it work offline?
After the page loads, yes. HTML, CSS, and JS are self-contained – disconnect Wi-Fi and keep checking.