Image Format Detector
Drop any image to see its real format, dimensions, and metadata. Detects true file type from magic bytes — 100% client-side, no upload.
About this tool
Not sure if that file is really a PNG or actually a WebP? Drop it here and this detector reads the file's magic bytes — the unique binary signature embedded in every image — to tell you the true format, regardless of what the filename claims. It also shows dimensions, MIME type, file size, and color depth. Everything runs in your browser: no upload, no server analysis, no privacy risk.
How to use it
Quick steps to get the most out of this utility.
- 1
Drop your image
Drag and drop any image file into the upload area, paste from clipboard, or click to browse.
- 2
Instant analysis
The tool reads the first 16 bytes of the file and compares them against known format signatures.
- 3
Review the report
See the true format, declared extension, MIME type, file size, dimensions, and magic bytes hex preview.
- 4
Copy or re-check
Use "Copy All Info" to save the report, or drop another image to analyze it.
Why file extensions lie — and how to know the truth
File extensions are a naming convention, not a guarantee. Rename photo.png to photo.jpg in any file manager and the icon changes — but the bytes inside do not. The browser, the operating system, and any image editor will still open it as a PNG because they read the file's header, not its name. This detector surfaces that truth: it reads the raw binary signature at the start of the file and reports what the data actually says.
A concrete example: someone sends you chart.png that won't open in your PNG-only tool. Drop it into this detector and you see the magic bytes are 52 49 46 46 ... 57 45 42 50 — the RIFF/WEBP signature. The file is actually a WebP image that someone (or some app) saved with a .png extension. Knowing this, you can convert it to PNG using a dedicated converter instead of troubleshooting a "corrupt" file that isn't corrupted at all.
How magic byte detection works
Every image format has a mandated sequence of bytes at position zero. PNG files start with 89 50 4E 47 (‰PNG). JPEG files start with FF D8 FF. GIF files start with 47 49 46 38 (GIF8). These are called magic bytes or file signatures, and they are required by the format specification — no valid image file exists without them. This detector reads the first 16 bytes of your file using the browser's FileReader API, compares them against a lookup table of 10+ format signatures, and reports the match. Because it happens entirely in your browser's JavaScript runtime, there is zero network activity.
Common scenarios where detection saves the day
iPhone HEIC photos arriving as .jpg email attachments, WebP images from design tools saved under .png filenames, AVIF files that a CMS renamed to .jpg, SVG icons exported as .png, and BMP screenshots mislabeled as TIFF — these are everyday realities for anyone who works with images across multiple platforms. The format detector identifies each one in under a second, tells you exactly what went wrong, and gives you the data you need to rename or convert the file correctly.
Why no-upload matters for image inspection
Images can contain sensitive content: personal photos, identity documents, private screenshots, medical scans, financial statements, or confidential business assets. Uploading an image to a "format checker" website means you are sending that private data to an unknown server, where it may be stored, indexed, or analyzed. This tool eliminates that risk entirely. It reads the file's header bytes directly in your browser tab using the standard FileReader API. No bytes ever travel over the network. The analysis is instant, private, and leaves no trace — just like any file inspection tool should operate.
| Feature | This tool | Upload-based detectors |
|---|---|---|
| Privacy | 100% client-side | File sent to a server |
| Speed | Instant (no upload wait) | Depends on network + queue |
| Formats detected | 10+ via magic bytes | Variable, often fewer |
| Extension mismatch flag | Yes, with amber warning | Rarely |
| Cost | Free, no sign-up | Sometimes freemium |
Frequently asked questions
Is this safe? Does it upload my image?+
No upload. The entire tool runs in your browser using JavaScript. Your image never leaves your device, never touches our server, and is never logged.
What image formats can be detected?+
The detector identifies PNG, JPEG, GIF, WebP, BMP, AVIF, SVG, ICO, HEIC, and TIFF — plus common variants like HEIF and JPEG 2000 precursor signatures.
What is the maximum file size?+
You can analyze images up to ~50 MB. Files over 25 MB will be slower, especially on mobile. For very large images beyond 50 MB, try reducing the file first.
Will this work on mobile?+
Yes, on modern iOS Safari and Chrome for Android. Very large images may be slow on older devices due to memory constraints.
How does format detection work?+
It reads the first 8–16 bytes of the file — called "magic bytes" — which are a unique signature hardcoded at the start of every image format. PNG always begins with 89 50 4E 47, JPEG with FF D8 FF, GIF with 47 49 46 38, and so on. These bytes are independent of the filename or extension.
What are magic bytes exactly?+
Magic bytes are a fixed sequence of bytes at the very beginning of a file that identify the format. Think of them as a file’s DNA — they are embedded by the software that creates the image and cannot be changed by simply renaming the file. Operating systems, browsers, and image libraries all rely on magic bytes, not file extensions, to determine how to decode a file.
Why would an image file have the wrong extension?+
Common scenarios: (1) Someone renamed a PNG to .jpg for compatibility with a website that only accepts JPEG, (2) an app saved a WebP file but retained the original .png filename, (3) a download manager stripped or altered the extension, or (4) a HEIC photo from an iPhone was mislabeled. In all cases, the image still opens because browsers read magic bytes, not the filename.
What are the most common format misidentifications?+
WebP files saved with a .png extension (happens often with browser-based image editors). iPhone HEIC photos arriving as .jpg attachments (email proxies sometimes alter extensions). SVG icons saved as .png after exporting from design tools. And renamed BMP files pretending to be JPEGs — the detector catches all of these.
Keep exploring
More utilities and reading from Toolisk.