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100% free · no signupRuns in your browser

Image Format Detector

Detect the true image format by inspecting magic bytes.

Best for: Use it when an image won't open or upload, or to verify a file's real type before converting or sending it.

Complete guide

Input

100% private — your file is processed in your browser and never uploaded.

How it's calculated & sources
The Image Format Detector uses the standard method for this calculation. It runs entirely in your browser, so your inputs are never uploaded. Last reviewed June 2026.

Free & no sign-up · runs entirely in your browser. Results are estimates for general information, not professional advice — verify important decisions with a qualified expert. Last reviewed June 2026.

Continue your journey

Where people usually head next.

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Image Compressor
Reduce JPEG file size by re-encoding at chosen quality — 100% in-browser.
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Image Resizer
Resize images to any width/height with optional aspect ratio lock.
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Image Converter
Convert images between PNG, JPEG and WebP in your browser.

Complete guide

Quick answers

Short, sourced answers to the questions people (and AI assistants) ask most.

What is Image Format Detector?
Image Format Detector identifies an image's true file type from its contents, not its extension - so a mislabelled file is exposed.
Why does Image Format Detector matter?
You learn what the file really is. A '.jpg' that is actually a PNG (or vice versa) can break uploads or conversions - this tells you the truth.
How is Image Format Detector calculated?
It reads the first few bytes (the magic number) in your browser and matches them to a format like JPEG, PNG, GIF, WebP or BMP.
What is a good image format detector?
Signatures: JPEG starts FF D8 FF; PNG 89 50 4E 47; GIF 'GIF8'; WebP 'RIFF....WEBP'; BMP 'BM'.
What are common image format detector mistakes?
Trusting the file extension, which anyone can rename.
When should you use the Image Format Detector?
Use it when an image won't open or upload, or to verify a file's real type before converting or sending it.

What is the Image Format Detector?

Image Format Detector identifies an image's true file type from its contents, not its extension - so a mislabelled file is exposed.

How the Image Format Detector works

It reads the first few bytes (the magic number) in your browser and matches them to a format like JPEG, PNG, GIF, WebP or BMP.

What's a typical value?

Signatures: JPEG starts FF D8 FF; PNG 89 50 4E 47; GIF 'GIF8'; WebP 'RIFF....WEBP'; BMP 'BM'.

Common mistakes to avoid

  • Trusting the file extension, which anyone can rename.
  • Assuming a preview thumbnail proves the format.
  • Ignoring a mismatch that later breaks an upload.

Keywords: format, magic, bytes, detect.

Runs entirely in your browser. Your image is not uploaded.

Reviewed by the Free Tools Galaxy editorial team · Updated June 2026 · Calculated privately in your browser.

Frequently asked questions

Is the Image Format Detector free to use?+

Yes. Every tool on Free Tools Galaxy is 100% free, runs in your browser and requires no signup.

How accurate is the Image Format Detector?+

Image Format Detector uses the standard image format detector formula in double-precision arithmetic, so the same inputs always produce the same result and you can verify any figure by hand. It is an educational estimate — real-world outcomes depend on your actual rates, rules and assumptions.

Do you store my inputs?+

No. The Image Format Detector runs entirely in your browser. Nothing is uploaded or saved to a server.

Can I use the Image Format Detector on mobile?+

Yes — the interface is fully responsive and works on phones, tablets and desktops.

What are common mistakes to avoid?+

The most frequent mistake is mixing units. Double-check your inputs use a single, consistent unit before clicking Calculate.

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Based on this tool, your recent activity and how others chain tools together.

Likely next step

🎨Color PickerTop match🗜️Image CompressorReduce JPEG file size by re-encoding at chosen quality — 100% in-browser.📐Image ResizerResize images to any width/height with optional aspect ratio lock.🔄Image ConverterConvert images between PNG, JPEG and WebP in your browser.✂️Image CropperCrop any image to a custom rectangle entirely in your browser.🔃Image RotatorRotate any image by any angle and download losslessly.

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Share-to-grow kit (Reddit, LinkedIn, Medium)
Reddit post
Title: I built/used this free image format detector — instant, no signup

Body: Detect the true image format by inspecting magic bytes. Try it: https://freetoolsgalaxy.com/tools/image-format-detector
LinkedIn post
Image Format Detector on Free Tools Galaxy — Detect the true image format by inspecting magic bytes. https://freetoolsgalaxy.com/tools/image-format-detector
Medium intro
# Image Format Detector — the free tool I keep coming back to

Detect the true image format by inspecting magic bytes.

Try it: https://freetoolsgalaxy.com/tools/image-format-detector
Quora answer
The fastest way is to use a free in-browser image format detector: https://freetoolsgalaxy.com/tools/image-format-detector. Detect the true image format by inspecting magic bytes.

Embed this tool anywhere

Free embed code for blogs, docs and dashboards. Every embed sends a backlink home — helping you and the galaxy grow together.

HTML iframe
Drop into any site — auto-resizes to its content height, theme-aware.
<iframe src="https://freetoolsgalaxy.com/tools/image-format-detector?embed=1" title="Image Format Detector" loading="lazy"
  style="width:100%;height:600px;border:0;border-radius:16px;background:#0b1020"
  allow="clipboard-write"></iframe>
<script>window.addEventListener("message",function(e){if(e.data&&e.data.type==="ftg-embed-height"){document.querySelectorAll("iframe").forEach(function(f){if(f.contentWindow===e.source){f.style.height=e.data.height+"px";}});}});</script>
<p><a href="https://freetoolsgalaxy.com/tools/image-format-detector" target="_blank" rel="noopener">Powered by Image Format Detector on Free Tools Galaxy</a></p>
Responsive wrapper
Aspect-locked container — good for blog post bodies.
<div style="position:relative;padding-bottom:75%;height:0;overflow:hidden;border-radius:16px">
  <iframe src="https://freetoolsgalaxy.com/tools/image-format-detector?embed=1" title="Image Format Detector" loading="lazy"
    style="position:absolute;inset:0;width:100%;height:100%;border:0" allow="clipboard-write"></iframe>
</div>
WordPress / Markdown
Paste in a custom-HTML block or markdown file.
[Image Format Detector — free online tool](https://freetoolsgalaxy.com/tools/image-format-detector)

<iframe src="https://freetoolsgalaxy.com/tools/image-format-detector?embed=1" width="100%" height="600" frameborder="0"></iframe>
Text link-back
Minimal credit link — best for sidebars and footers.
<a href="https://freetoolsgalaxy.com/tools/image-format-detector" target="_blank" rel="noopener">Try the free Image Format Detector</a>

Share-to-Grow Kit

Pre-written, ready-to-paste posts for every major channel. Help others discover this tool — and earn backlinks.

Title
I built a free fraction calculator that works instantly in the browser — no signup, no ads in your face
Body
Hey r/[subreddit],

I kept needing a quick fraction calculator and most options online were slow or behind paywalls, so I built one that:

• Runs 100% in your browser (your data never leaves your device)
• No signup, no email wall, no popups
• Loads in under a second on mobile

It covers the standard fraction use cases (fraction, math) and links out to the formula + worked examples if you want to learn the math.

Link: https://freetoolsgalaxy.com/tools/fraction-calculator

Happy to take feedback — what's missing?
Post to a relevant subreddit (e.g. r/InternetIsBeautiful, r/webdev, r/productivity). Avoid spammy subs.
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