.pdfSafe
Portable Document Format, a universal layout-preserving document format.
Compatible Apps
Adobe Acrobat Reader, Microsoft Edge, Apple Preview, Google Chrome
File & Format Hub
Understand Any File Format
Search file extensions, explore file formats, and compare file types in one place.
No search history saved. Extension and format data reviewed weekly.
Reference
Popular File Extensions
Common extensions with compatible software and safety guidance.
.docxSafe
Microsoft Word Open XML document format used for editable text documents.
Compatible Apps
Microsoft Word, Google Docs, LibreOffice Writer, Apple Pages
.jpgSafe
Common lossy raster image format optimized for photographs and web graphics.
Compatible Apps
Apple Photos, GIMP, Adobe Photoshop, Windows Photos
.zipCaution
Widely used lossless compression and archive container.
Compatible Apps
7-Zip, WinRAR, macOS Archive Utility, Windows File Explorer
.pngSafe
Lossless raster image format with transparency support.
Compatible Apps
Apple Preview, GIMP, Adobe Photoshop, Google Chrome
.mp3Safe
Common lossy audio format used for music and spoken-word recordings.
Compatible Apps
VLC Media Player, Apple Music, Windows Media Player, Audacity
Formats
Explore File Formats
Reviewed format records with attributes, use cases, and related comparisons.
PDFdocuments
Fixed-layout document format for reliable sharing, printing, and long-term records.
PNGimages
Lossless raster image format with full alpha transparency and universal support.
JPEGimages
Lossy raster image format optimized for photographs with universal compatibility.
WebPimages
Modern image format with lossy and lossless modes, transparency, and animation.
SVGimages
Open vector image format that scales crisply at any size and is editable as text.
CSVdata
Plain-text tabular format understood by spreadsheets, databases, and data pipelines.
XLSXdocuments
Standard spreadsheet format for formulas, tables, charts, and multi-sheet workbooks.
DOCXdocuments
Word processing format designed for editing, collaboration, and Microsoft Office.
Compare
Popular Comparisons
Side-by-side criteria and conditional verdicts for common format decisions.
PNG vs JPEGThe classic image decision: lossless pixels with transparency versus small, lossy photos.images pairWebP vs AVIFNext-generation web image formats compared for compression, transparency, and tooling.images pairMP4 vs WebMUniversal MP4 versus open WebM for streaming and web video delivery.video pairPDF vs DOCXFixed-layout delivery versus editable office documents for sharing and collaboration.documents pairCSV vs XLSXPlain tabular text versus a full spreadsheet workbook with formulas, formatting, and multiple sheets.data pair
Categories
Browse by Category
Formats, extensions, comparisons, and guides grouped by content type.
Guides
Practical Guides
How to open unknown files, choose formats, and compare trade-offs.
Guide
How to Open Unknown Files
4 min read
Guide
How to Show File Extensions
4 min read
Guide
File Extension vs. File Format
3 min read
Guide
Is an Unknown File Safe?
5 min read
Guide
How to Choose a File Format
6 min read
Guide
Lossy vs Lossless Formats
5 min read
Guide
Vector vs Raster Images
6 min read
Guide
Open vs Proprietary Formats
7 min read
FAQ
Frequently Asked
What is a file extension?
A file extension is the suffix after the final period in a filename, such as .pdf, .jpg, or .docx. It tells operating systems and users which file type the name refers to, but it is not the same as the file format inside the bytes.
How do I open a file with an unknown extension?
Search for the extension here first so you can see what it represents and which compatible applications can open it. Then download software from the publisher or a known official source and use that application to open the file.
Can changing a file extension convert the file?
No. Renaming photo.png to photo.jpg changes only the label. The image data remains PNG until a converter decodes it and writes a new file in the target format.
Is it safe to download files with uncommon extensions?
Not necessarily. Attackers can use uncommon or misleading extensions to disguise malicious files. Verify the source, scan the file, and never open executable formats such as EXE, BAT, or MSI from untrusted sources.
How often is the extension database updated?
The reviewed dataset is updated weekly. Each record includes a reviewed date and source links so you can see when the information was last checked.
Why does a download finish as a CRDOWNLOAD file?
CRDOWNLOAD is a partial download marker used by Chromium browsers. It becomes the final filename only after the download completes; resume or restart the download instead of renaming the file.