FastImageToolsFastImageTools

Image Extension Mismatch Checker

Compare a known filename extension with the image format detected from the file signature. The inspection runs locally in your browser, and the original file is not uploaded by this tool.

Local processingJSON reportNo sign-up

Drag & drop your images

or click below to browse your files

JPGPNGWebPAVIFGIFSVGHEICTIFFBMPRAW
⌘VPaste from clipboard
•Drag from Finder or Photos

Free users: up to 15 images at once • Premium: unlimited batch processing

Back to Inspect Image Format, Metadata, and Compatibility

What this inspection checks

Compare a known filename extension with the image format detected from the file signature.

The report shows the detected container, the supplied extension and MIME type, and an explicit mismatch warning when both formats are known and disagree.

How to inspect the image

  1. 1

    Choose an image

    Select one or several supported image files from your device.

  2. 2

    Review the detected fields

    Open the format details and integrity tabs to review the values found in the file structure.

  3. 3

    Keep the result

    Copy the report or download it as JSON. The original image is not changed.

Frequently asked questions

What does this checker report?

The report shows the detected container, the supplied extension and MIME type, and an explicit mismatch warning when both formats are known and disagree.

Is my image uploaded?

No. This inspection runs in your browser and does not upload the original image.

Does the checker modify the image?

No. It reads technical fields and produces a report; it does not convert, repair, or rewrite the file.

Is the result a complete file validation?

An unknown extension is not treated as a mismatch. ICO and CUR are not currently parsed, and this check does not prove that every byte in a file is valid.

Related image tools

JPG Format Inspector

Inspect JPEG container and encoding details without decoding or changing the picture.

PNG Format Inspector

Inspect PNG color type, bit depth, transparency, interlace, profile, text, and APNG information.

Image Bit Depth Checker

Read the encoded bit depth reported by supported raster image structures.

Progressive JPEG Checker

Check whether a JPEG uses progressive scans or baseline encoding.

PNG Transparency Checker

Check whether a PNG encodes transparency through an alpha channel or a tRNS chunk.

GIF Frame Counter

Count frames in a GIF and inspect its animation timing, loop setting, palette, and transparency.

We value your privacy

FastImageTools uses essential cookies for core functionality.

With your consent, we also use analytics (Google Analytics) and advertising cookies (Google AdSense). You can accept all cookies, reject non-essential cookies, or manage your preferences at any time.

Privacy Policy | Cookie Policy