File Extensions Guide & File Types Directory
What does .PDF, .HEIC, .ZIP, .EXE or .JSON mean? Search common file extensions, understand what each format is for, find programs that can open it and learn when to be cautious.
Reference guide only. A file extension is a useful clue, not proof of a file’s contents, safety or the exact app required. Some extensions belong to multiple unrelated formats.
Find a file type
Search by suffix, description or typical use, then filter by category.
Know what opens it
Each entry suggests the kind of app needed to view or edit the format.
Handle files safely
Read format-specific warnings before running scripts or opening unexpected attachments.
What is a file extension?
A file extension is the ending of a filename, usually following the last dot. In holiday-photo.jpg, the name is holiday-photo and the extension is .jpg. It helps the operating system suggest which apps can open the file. The actual file format also depends on the data stored inside, not merely its name.
Extensions are handy shortcuts: .pdf often means a document intended to retain its layout, .mp3 commonly means compressed audio, and .zip indicates an archive that may hold many files. Some endings are ambiguous, so the creating app and the file’s content may matter as much as the suffix. This directory also includes a few special dotfiles (such as .gitignore) and compound filename endings (such as .tar.gz); these are useful to recognize but are not all single, standalone file extensions.
picture.jpg to picture.png does not convert JPEG into PNG. Use an export or conversion feature instead.The main families of file formats
Different formats solve different problems. Documents prioritize readable pages or editable text, images preserve pictures and illustrations, audio/video formats handle recorded media, and archives bundle or compress several files. Software packages, scripts, project files and structured datasets serve more specialized purposes.
Documents and office files
PDF is useful when layout must stay consistent. DOCX, ODT and PPTX are better when someone needs to edit the content.
Images and design files
JPEG is efficient for photographs; PNG works for lossless screenshots; SVG keeps vector graphics scalable; PSD saves editable layers.
Audio and video
MP3 and AAC are popular compressed audio formats. MP4 and MKV are containers, so the codecs inside affect playback.
Archives and disk images
ZIP and 7Z can package many files; TAR usually bundles them; ISO and DMG represent disk or installer images.
Developer and data formats
JSON, YAML and XML structure data. HTML, CSS, JS and Python files contain code or markup, while CSV and Parquet store tables.
Apps and system components
EXE, APK, MSI, DEB and scripts can install or execute programs; DLL and SYS are generally used by operating systems and applications.
How to choose the right file format
Start with what the recipient needs to do. Are they reading, editing, printing, playing or processing the file? A broadly supported format is usually preferable for sharing, while a native project format is better when someone needs layers, formulas, animation timelines or editable design objects.
| Goal | Often useful | Why |
|---|---|---|
| Send a finished document | Preserves visual layout | |
| Collaboratively edit text | DOCX / ODT | Supports text editing and styles |
| Share a photograph | JPG / WEBP | Efficient image sizes |
| Share a logo | SVG / PNG | Scalability or transparency |
| Exchange simple table data | CSV | Readable by many data tools |
| Bundle several files | ZIP | Widely available extraction support |
These are practical starting points, not universal rules. Accessibility, licensing, recipient software and quality needs can change the recommendation.
How to open unknown files more safely
Files arriving by email, chat or download can be mislabeled. Before opening an unfamiliar attachment, check who sent it, whether you expected it, and whether its type makes sense. Viewing an image or document can also carry risks if the software has a vulnerability, so keeping apps updated matters.
- Show filename extensions. On your operating system, enable visible extensions so a name like
invoice.pdf.exeis less misleading. - Check the source. Confirm unexpected requests through a separate trusted channel.
- Inspect before you run. Do not execute unfamiliar EXE, BAT, CMD, PS1, SH or installers.
- Avoid enabling macros. Office documents may request macros or active content that you do not need.
- Use trusted software. Keep your system and viewer updated and use built-in malware protections.
- Keep backups. Maintain copies of important files before installing, importing or converting unknown data.
File conversion, compression and compatibility
A converter reads one format and exports another. It might remove details that the target cannot support: converting a layered Photoshop project into PNG flattens its layers, while converting a spreadsheet into CSV loses formulas, charts and multiple sheets. Always keep the editable original when future changes are likely.
Compression is not always conversion. ZIP creates an archive that contains your original files; JPEG and MP3 usually reduce size by permanently discarding some image or audio information. Formats such as PNG and FLAC preserve the encoded information losslessly, though they serve different media needs.
Compatibility also depends on the actual encoding inside a file. For example, two .mp4 files may use different video codecs, so one plays on a device while the other does not. When sharing across platforms, test an exported copy with the intended reader or recipient app.
File extension vs. MIME type vs. file signature
A file extension is part of a filename. A MIME type (media type), such as application/pdf or image/png, is a label software and web servers can use to describe content. A file signature is a recognizable sequence of bytes inside some formats that helps identify what the data probably is.
These clues can disagree. A download may be named report.pdf even if its bytes are not a PDF. A web server may also send an incorrect media type. Reliable identification uses more than a suffix, and malware scanning still matters regardless of labels.
Common file extension mistakes
Changing the suffix to convert
Renaming .png to .jpg does not convert pixels into JPEG coding. Export the desired file format instead.
Assuming ZIP files are safe
An archive can contain unsafe executables or scripts. Review its contents before running anything.
Confusing container and codec
MP4 and MKV describe containers; the audio/video streams inside can use different codecs.
Expecting every editor to work equally
An app may open a format but lose layers, complex formatting or advanced features on export.
Frequently asked questions
How do I find a file extension?
Look at the text after the final dot in a filename, such as .pdf in report.pdf. Some operating systems hide extensions by default, so enable their display in file settings.
Can I open every file in a web browser?
No. Browsers can display many web documents and media formats, but specialized projects, system files and unsupported codecs need other software.
What is the difference between JPG and PNG?
JPG usually uses lossy compression that works well for photos. PNG uses lossless compression and is useful for screenshots, graphics and transparency.
Are .exe and .apk files dangerous?
These formats are software packages that can run code. They are not inherently malicious, but files from unfamiliar or untrusted sources carry risks.
What happens if I delete a file extension?
The file data usually remains unchanged, but your system may no longer know which application to open by default. You can often restore the correct suffix.
Can a file have more than one extension?
Yes. A filename may end in .tar.gz for a gzip-compressed TAR archive. Double extensions can also be misleading, as in photo.jpg.exe, which is an executable on Windows.
Are file extensions case sensitive?
Many systems treat .JPG and .jpg similarly, but case sensitivity can vary by operating system, filesystem and application.
What if an extension has more than one meaning?
Use the source application, trusted documentation and file contents to identify the format. Some short extensions have unrelated uses.
Is this guide a file scanner or converter?
No. It is a searchable learning reference. It does not read, scan, upload, open or convert your files.
Do I need to upload a file to use this tool?
No. Searching and filtering the built-in directory happens in your browser without uploading files.