File Type Checker
File extensions can lie. This tool reads the file's first bytes (the magic number) and reports the real format — useful for security checks, recovered files, and mystery downloads.
Input
*
Output
INFO
Max size
200MB
Files
1 at a time
You might also need
JSON to CSV
Paste JSON or upload a file. Headers are detected from your object keys, nested values are flattened with dot notation, and the CSV downloads instantly.
CSV to JSON
Upload or paste CSV data. The first row becomes object keys; each subsequent row becomes an object. Download as a clean JSON array.
Compress Image
Shrink images for the web, email, or storage. Smart compression and optional resizing reduce file size dramatically while keeping the result visually clean.
Merge PDF
Stitch up to 20 PDFs into a single document. Drag to reorder, see total page counts, and download instantly. All merging is done locally in your browser.
Frequently Asked Questions
How does file-type detection work?
Most file formats begin with a unique sequence of bytes called a 'magic number'. We read the first 16 bytes and match them against a lookup table of known formats.
Why might the extension be wrong?
Extensions are just labels — anyone can rename a file. Detected types reflect what the file actually is, which matters for security, debugging, and data recovery.
What formats can it detect?
20+ common types including PNG, JPG, GIF, WebP, PDF, ZIP, MP4, MP3, MKV, BMP, TIFF, GZIP, FLAC, OGG, and Office documents (DOCX/XLSX/PPTX).
Is my file uploaded for analysis?
No. Detection happens by reading the first few bytes locally in your browser. The file never leaves your device.
What does it report?
Detected type, MIME type, file size, last modified date, and (for images) dimensions. If the extension and detected type disagree, you'll see a warning.