File extensions tell you what type of file something is and what can open it. When you see .heic and nothing opens it, or you get a .webp and need a .jpg, the extension is your first clue about what to do. Here's a plain-English reference for the most common ones — and what to do when a format causes problems.
Quick answer: The format you can't open almost always has a browser-based converter that handles it in seconds. The most common problems: HEIC (iPhone photos) → convert to JPG; WebP (website images) → convert to JPG/PNG; MKV/WebM (videos) → convert to MP4.
Why do file extensions even exist?
File extensions tell your operating system which application to use when you open a file. When an app saves a file in its own format, it adds an extension so the OS knows how to handle it later. The problem is different operating systems and apps support different formats — so a file created on an iPhone can fail to open on a Windows PC.
What are the main image formats?
JPG / JPEG
The standard photo format. Used by cameras, smartphones, and most of the web. Uses lossy compression — some quality is sacrificed to keep file sizes small. Fine for photos, bad for screenshots with text. JPG files can be combined into a single document using a JPG to PDF converter — useful for sending scanned pages.
PNG
Lossless format — keeps every pixel perfectly. Larger files than JPG. Supports transparency. Best for screenshots, logos, icons, and graphics with sharp edges. If PNG files are too large for sharing, an image compressor can reduce their size without changing the format.
WebP
Google's modern format. Smaller than JPG and PNG at equivalent quality. Supports transparency and animation. Works in all modern browsers. Increasingly common on websites.
HEIC / HEIF
Apple's format used by iPhones. Better compression than JPG (half the file size). Not supported by Windows or Android without extra software. Convert to JPG for sharing.
GIF
Old format for simple animations. Limited to 256 colors. Still widely used for short looping animations (memes, reactions). WebP and MP4 are technically better but GIF remains universal.
SVG
Vector format, not a photo. Stores images as mathematical shapes, not pixels. Scales to any size without quality loss. Used for logos, icons, and illustrations. Small file size.
TIFF / TIF
High-quality lossless format used in professional photography and printing. Very large files. Not suitable for web use. Used in professional workflows.
BMP
Old Windows format. Uncompressed, so files are enormous. No reason to use it for new work. Occasionally encountered on old Windows systems.
RAW (CR2, NEF, ARW, etc.)
Unprocessed image data directly from a camera sensor. Different camera brands use different RAW formats. Very large files. Requires specialized software or conversion to JPG/TIFF for general use.
What are the main document formats?
Portable Document Format — the universal document format. Looks the same on every device. Can't be accidentally edited. Supports encryption. The right choice for sharing final documents.
DOCX
Microsoft Word's current format. Can be edited in Word, Google Docs, LibreOffice. Contains text, images, formatting, and can include tracked changes.
DOC
Older Microsoft Word format (pre-2007). Still opened by modern Word and most alternatives, but DOCX is preferred.
XLSX
Microsoft Excel spreadsheet format. Can be opened in Excel, Google Sheets, LibreOffice Calc.
PPTX
Microsoft PowerPoint presentation format. Contains slides, animations, and embedded media.
TXT
Plain text. No formatting. Opens in any text editor on any operating system. The simplest document format.
EPUB
E-book format. Used by most e-readers. Reflowable text — fonts and layout adapt to screen size.
What are the main video formats?
MP4 (H.264)
The standard video format. Plays everywhere — web, phones, TVs, computers. If you're sharing video, MP4 is almost always the right choice.
MKV
Matroska container. Popular for storing high-quality movies. Can contain multiple audio tracks and subtitles. Convert to MP4 for better compatibility.
WebM
Google's web video format. Used for videos embedded in websites. Convert to MP4 for broad compatibility.
MOV
Apple's QuickTime format. Works great on Macs. On Windows, you might need QuickTime installed. Usually convertible to MP4 easily.
AVI
Old Microsoft format. Large files, outdated. You'll encounter it with old media. Convert to MP4.
I've seen this cause confusion constantly at work — someone records a meeting on a Mac and shares a .mov file, then half the team can't play it on Windows. Converting to MP4 takes about 2 minutes and eliminates the problem entirely.
What are the main audio formats?
MP3
The universal audio format. Works everywhere. Lossy compression. 128 kbps is fine for speech; 192-320 kbps for music.
WAV
Uncompressed audio. Perfect quality. Very large files (10x larger than MP3). Used for music production, audio editing.
FLAC
Free Lossless Audio Codec. Perfect quality (lossless), but smaller than WAV. Popular among audiophiles. Not supported everywhere.
AAC / M4A
Better compression than MP3 at the same quality. Used by Apple (iTunes, iPhone default). Common for recordings from iPhone. Convert to MP3 for universal compatibility.
OGG / VORBIS
Open-source alternative to MP3. Common in games and web apps.
What are the archive formats?
ZIP
Universal archive format. Supported natively by Windows and Mac. No extra software needed to open.
RAR
More compressed than ZIP but requires WinRAR or 7-Zip to open.
7Z
Open format with better compression than ZIP. Requires 7-Zip or similar to open.
Quick reference table
| Extension | Type | Universal? | Notes |
|---|---|---|---|
| JPG | Image | Yes | Photos |
| PNG | Image | Yes | Graphics, screenshots |
| WebP | Image | Modern browsers | Smaller than JPG |
| HEIC | Image | Apple only | Convert to JPG for sharing |
| MP4 | Video | Yes | Use this for video sharing |
| MP3 | Audio | Yes | Standard audio |
| Document | Yes | Final documents | |
| DOCX | Document | Yes (with apps) | Editable documents |
| ZIP | Archive | Yes | Compressed files |
This covers the formats most people encounter day-to-day. When you see something unfamiliar, the file extension is your first clue — and most can be converted to a more compatible format quickly using a browser-based file converter that handles images, PDFs, audio, and video without uploading your files.
Frequently asked questions
What's the most common format problem people run into? HEIC files from iPhones not opening on Windows. The fix is either installing the free HEIF extension from the Microsoft Store, or converting HEIC to JPG in a browser tool — which takes about 5 seconds per file.
Is this completely free? Yes — no account, no payment, no watermark needed. You can use it as many times as you want.
Do my files get uploaded to a server? No. Browser-based converters run entirely in your browser using WebAssembly. Your files never leave your device.