Check if Image is PNG Online Tool
Check If Image is PNG reads the 8-byte signature, IHDR, colour type, APNG animation, and IEND trailer.
Drop a file in and get a byte-level verdict: PNG or not, colour type, dimensions, interlace, APNG animation, and IEND trailer — all in your browser.
Click to upload or drag and drop
Any file — the tool reads the first 64 KB + last 12 bytes locally, regardless of extension
Details
First 14 bytes (hex)
A PNG always starts with the 8-byte signature 89 50 4E 47 0D 0A 1A 0A and ends with the 12-byte IEND chunk.
How to Use Check if Image is PNG Online Tool
- Drop any file onto the upload area - the extension is ignored. The tool reads the first 64 KB plus the last 12 bytes locally, so even huge files open instantly.
- Read the verdict: green means PNG (with colour type and APNG hint); amber means not a PNG, with the reason shown.
- Scan the details card: width, height, bit depth, colour type (Greyscale / RGB / Indexed / Greyscale+α / RGBA), interlace (None or Adam7), palette, ICC profile, sRGB tag, transparency hint, and APNG frame count.
- Eyeball the hex line: the first 14 bytes in uppercase hex. A real PNG always starts with
89 50 4E 47 0D 0A 1A 0A. - Check the IEND trailer row: a truncated PNG will keep its signature but lose the
IENDchunk at the end. The tool flags this clearly. - Press
Ctrl+Enter(⌘+Enteron Mac) to re-run the check on the last file - useful after a re-save. - Copy the plain-text report or Download a timestamped `.txt` that embeds the original filename.
Frequently asked questions
Is my file uploaded anywhere?
No. The entire check runs in your browser. Only the first 64 KB and the last 12 bytes are ever read, via File.slice().arrayBuffer() – the file never leaves your device.
How does the tool detect PNG format?
It verifies the first eight bytes match the PNG signature 89 50 4E 47 0D 0A 1A 0A, then walks chunks to read the IHDR and scan for tRNS, acTL (APNG), PLTE, iCCP, sRGB, and IDAT.
Does it detect renamed files?
Yes. The extension and reported MIME type are ignored – only the real bytes decide. A PNG renamed to photo.jpg is still identified as PNG.
What if my file has a .png extension but isn’t PNG?
Reported as “Not a PNG” with the reason shown. The tool never consults the extension or MIME type.
What do the colour types mean?
PNG supports five colour types: 0 (Greyscale), 2 (Truecolor/RGB), 3 (Indexed/palette), 4 (Greyscale + Alpha), and 6 (Truecolor + Alpha / RGBA). The details card labels whichever one your file uses and the associated channel count.
What is APNG?
Animated PNG – an extension that adds an acTL chunk before IDAT plus fcTL / fdAT frame chunks. The tool detects the acTL and reports frame count and play count (0 = infinite).
Why does the tool mention “transparency hint”?
A PNG has transparency if either (a) the colour type is 4 or 6 (alpha channel), or (b) a tRNS chunk gives simple transparency for indexed or RGB files. The hint flag is on when either condition holds.
What’s interlace?
PNG supports two interlace methods: None (0) or Adam7 (1). Adam7 splits the image into seven progressive passes so it appears sooner on slow connections, at the cost of a slightly larger file.
Is there a file size limit?
No. Only the first 64 KB and the last 12 bytes are read, so file size does not matter for the check itself.
Does it work offline?
After the page loads, yes. HTML, CSS, and JS are self-contained – disconnect Wi-Fi and keep sniffing.