140 file extensions
Find out what a file is and what opens it, starting from the extension — with its MIME type and whether a browser can open it directly.
Images21
Formats that hold photos and drawings. The same picture can differ hugely in size and quality depending on the format.
Video14
Moving pictures with sound. The extension only names the container — what actually plays depends on the codec inside.
Audio12
Sound only. These split into formats that throw audio away to shrink the file and formats that keep every sample.
Documents18
Text, tables and slides. Many have open standards so they can be read outside the program that made them.
Archives12
Several files bundled into one and squeezed smaller. Until you extract it, you only see the list of what is inside.
Code22
Source files people read and write. Inside they are plain text, so even Notepad opens them.
Data10
Tables and records. These are what you use to move values between programs.
Subtitles4
Captions laid over video. They are text files pairing timestamps with lines, so you can edit them yourself.
Fonts5
The shapes of letters. Install one and every program on the machine can use it.
E-books4
E-book formats. Unlike paper, the text reflows to fit whatever screen you read it on.
3D models6
Three-dimensional shapes — the formats 3D printers and game engines read.
Disk images4
A whole disc captured as one file. Open it and it mounts just like the original disc.
Programs8
Programs themselves, or their installers. If you do not know where one came from, do not open it.
How to read this
- An extension is a label, not the contents. Rename a file to .png and if the bytes inside are JPEG, it is still a JPEG.
- A MIME type is how the internet names a file kind. Browsers look at that value, not the extension, to decide whether to display or download.
- A MIME type starting with x- was never registered as a standard. Plenty are in wide use, but they are not official names.
- Video extensions name a container. The same .mp4 may play on one device and not another, depending on the codec inside.
Frequently asked questions
Q. Does renaming the extension change the format?
No. The extension is only a label; the bytes inside stay exactly as they were. Rename a JPEG to .png and it is still a JPEG — and programs that check the real format may now refuse to open it. To truly change format you have to convert and re-save.
Q. My extensions are hidden — how do I see them?
In Windows Explorer, turn on "File name extensions" in the View menu. On macOS, tick "Show all filename extensions" in Finder settings. They are hidden by default, which is exactly how names like photo.jpg.exe fool people.
Q. Is it safe to open a file type I do not recognise?
Treat executables (.exe, .msi, .apk, .jar) as unsafe unless you know where they came from. Documents and archives can carry executables inside too, so scan anything whose source you cannot vouch for.
Q. What is a MIME type for?
It is the label a web server sends along with a file to say "this is image/png". Browsers trust that value rather than the extension when deciding whether to render or download, so a wrong MIME type shows an image as garbled text or forces a download.
Q. Why do some formats have two extensions?
Because of history. .jpg and .jpeg are the same format with the same MIME type, image/jpeg — the short form exists because early DOS allowed only three letters. The same goes for .sqlite and .db, or .mpg and .mpeg.