Open a file with no extension
Drop the file below to see what it really is and open it. Its type is read from its bytes, not its name. Your browser opens it on your device: nothing is uploaded.
First bytes it looks for
| Starts with | Format |
|---|---|
89 50 4E 47 | PNG |
FF D8 FF | JPG |
47 49 46 38 | GIF |
52 49 46 46 … 57 45 42 50 | WebP |
25 50 44 46 | PDF (%PDF) |
50 4B 03 04 | ZIP, and so DOCX, XLSX and PPTX |
… 66 74 79 70 | MP4, MOV, M4A, HEIC, AVIF (ftyp) |
1A 45 DF A3 | WebM, MKV |
49 44 33 | MP3 (ID3) |
52 49 46 46 … 57 41 56 45 | WAV |
4F 67 67 53 | OGG |
66 4C 61 43 | FLAC |
D0 CF 11 E0 | Old Office files: DOC, XLS, PPT, MSG |
| Text | JSON, XML, SVG, HTML, CSV and YAML from their first lines |
How to open a file with no extension
Drop it in the box above. The viewer reads its first bytes, where most formats write a signature, and opens it as a picture, video, PDF, document, table or archive. Details names the extension to give it. Nothing is uploaded.
The name of a file is only a label. A PNG renamed img is still a PNG inside: it begins with the bytes 89 50 4E 47. Word and Excel files are ZIPs, so the viewer looks inside for their parts; text formats are recognised from their first lines. The same works for a file with the wrong extension, such as a .jpg that is really a WebP.
When you send the file on with Open in, the other tool gets a copy with the right extension, and Download inside an archive does the same.
Questions
Drop it on the viewer. It reads the first bytes, where most formats keep a signature, and opens the file as what it is. Details names the format and the extension it should have.
Rename the file and add the extension Details gives, such as .png or .pdf. On Windows, turn on File name extensions under View in File Explorer first, or the new ending is hidden.
Chat apps, email gateways, cloud exports and some downloads strip or replace it, and Windows hides extensions by default, so a renamed file can end up with none, or with two.
It opens as bytes, in a hex view. The first bytes often name the program that made it.
No. It is read in your browser, on your device.