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Upload a file to verify whether it is a real PNG (by file signature, not just the .png extension).

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Check PNG — verify PNG file type

Check PNG online free. Verify if an image is a real PNG file (not just renamed). Detect JPEG, WebP, GIF and more—PNG file type checker in your browser.

What is a check PNG / PNG file type checker?

A check PNG tool (PNG checker / test PNG verifier) confirms whether a file is a real Portable Network Graphics image by reading its binary signature—not the .png extension. People search for “check png”, “checker png”, “test png”, “error png”, and “what is a png file type” when uploads fail or a download looks wrong. This free online tool detects PNG vs JPEG, WebP, GIF, and more, shows IHDR details for valid PNGs, and runs entirely in your browser. For transparency testing, use Check If PNG Is Transparent instead.

PNG checker features

Verify PNG file type without trusting the extension.

  • Signature verification

    Reads the official 8-byte PNG magic header.

  • Real format detection

    Identifies JPEG, WebP, GIF, BMP, ICO, or SVG when it is not PNG.

  • IHDR details

    Shows width, height, bit depth, and color type for valid PNGs.

  • Preview

    Displays the uploaded image when the browser can decode it.

  • Private

    No upload—bytes never leave your device.

How to check a PNG file

Verify PNG format in a few steps.

  1. Upload the file

    Drop any image that might be a PNG (15 MB max).

  2. Read the result

    See whether the signature confirms PNG or another format.

  3. Review details

    For valid PNGs, check dimensions and color type.

  4. Fix if needed

    Convert or re-export, then test PNG again.

Tips for checking PNG files

Avoid common PNG file type mistakes.
  • 01

    Do not trust the extension

    Always verify with a signature check before shipping assets.

  • 02

    Transparent but not PNG?

    WebP can have alpha too—convert to PNG if the target app requires it.

  • 03

    Truncated downloads

    A PNG signature with a broken IHDR usually means an incomplete file.

  • 04

    Need transparency QA next?

    After confirming PNG, open Check If PNG Is Transparent.

PNG checkers compared

How this free check PNG tool stacks up against common alternatives.

  • Online PNG Tools (verify if image is PNG)

    Competitor ranking #1 for “check png” and “checker png”. Similar signature-based verification. This page also surfaces IHDR details and related converters.

  • file / magika CLI

    Great for scripts. Less convenient when you just need a quick browser check.

  • Trusting the file name

    Fast but wrong whenever someone renames .jpg → .png. Magic-byte checking avoids that failure mode.

  • This check PNG tool

    Private, free, clear PNG vs other-format results. Best for verify PNG file type workflows in the browser.

Great for

When a download or upload insists on a real PNG.

  • Debugging upload errors

    Find out why an app rejects your “PNG”.

  • Extension lies

    Catch JPEG/WebP files renamed to .png.

  • Asset QA

    Confirm handoff files are true PNG before shipping.

  • Learning the format

    See what a PNG file type looks like under the hood.

Why use this PNG checker

Fast, free, private PNG file type verification.

  • 100% free

    No sign-up and no limits on checks.

  • Privacy first

    Your file never leaves the browser tab.

  • Extension-proof

    Magic bytes beat filenames every time.

  • Actionable

    Learn the real format so you know how to convert.

Technical details

How this verify-if-image-is-PNG checker works.
PNG signature
89 50 4E 47 0D 0A 1A 0A at byte offset 0.
IHDR parse
Reads width, height, bit depth, and color type from the first chunk.
Other formats
JPEG SOI, GIF87a/89a, RIFF/WEBP, BMP “BM”, ICO, SVG text sniff.
Limits
15 MB; 100% client-side ArrayBuffer inspection.

Sources & References

Authoritative references on the PNG file format and magic-number detection.
  • “The first eight bytes of a PNG file always contain the following values: 137 80 78 71 13 10 26 10.”
    — PNG Specification — File structure

    PNG file signature: A reliable check PNG / PNG checker reads this signature instead of trusting the .png file extension. libpng.org/pub/png/spec/1.2/PNG-Structure.html

  • “PNG is a raster-graphics file format that supports lossless data compression.”
    — Wikipedia — PNG

    Portable Network Graphics: Knowing what a PNG file type is helps when downloads are mislabeled as .jpg or .webp. en.wikipedia.org/wiki/PNG

  • “The IHDR chunk contains image dimensions and basic color/bit-depth information.”
    — PNG Specification — Chunks

    IHDR chunk: After confirming the signature, this tool reads IHDR for width, height, bit depth, and color type. libpng.org/pub/png/spec/1.2/PNG-Chunks.html#C.IHDR

  • “Magic numbers are constant numerical or text values used to identify file formats.”
    — Wikipedia — File format

    File format magic numbers: JPEG, GIF, WebP, BMP, and ICO each have their own signatures—useful when a “PNG” upload is actually another type. en.wikipedia.org/wiki/List_of_file_signatures

Frequently Asked Questions

Quick answers about this tool—open a question to read more.