Best File Formats Explained: When to Use JPG, PNG, PDF, MP3, MP4, ZIP & More

Why file formats matter

The format you choose decides how big your file is, how good it looks (or sounds), and whether the person on the other end can even open it. Pick wrong and you'll end up with a 50 MB email attachment, a blurry logo, or an audio file that won't play on someone's phone. This guide is the no-jargon reference we wish we had when starting out.

Image formats

JPG / JPEG

The default for photos. Lossy compression, tiny file sizes, no transparency. Use it for camera photos, hero banners, and anything you'll post on social media. Quality dial: 90% is visually identical to lossless on most photos; 80% is great for the web; below 70% starts to show artifacts in skies and skin.

PNG

Lossless and supports transparency. Use it for logos, icons, screenshots, and any graphic with sharp edges. Avoid for photos — file sizes get huge fast. Tip: PNG-8 (256 colors) is dramatically smaller than PNG-24 for simple icons.

WebP

Google's modern format that's 25–35% smaller than JPG/PNG with the same quality. Universally supported in 2026. Best for the web — but some legacy desktop apps still won't preview it. See our JPG-to-WebP guide.

SVG

Vector format — infinitely scalable without losing quality. Ideal for logos, icons, charts, and illustrations. Useless for photos. Beware: SVGs can contain JavaScript, so only embed SVGs from sources you trust.

HEIC

Apple's iPhone format. Roughly half the size of JPG at the same quality, but Windows and many older apps can't open it. Convert to JPG before sharing widely — see our HEIC-to-JPG guide.

AVIF

The next-generation web format — about 50% smaller than JPG at the same quality. Use when you control the entire delivery pipeline. Older email clients and a few CMSes still don't handle it.

Document formats

PDF

The universal "this looks the same everywhere" format. Use for contracts, invoices, resumes, forms, and anything that should print exactly as designed. Our converter handles every common PDF transformation — to/from Word, JPG, PNG, Excel — entirely in your browser.

DOCX

Microsoft Word's editable format. Perfect when the recipient needs to make changes. Convert to PDF before sending the final version with our Word to PDF converter.

TXT

Plain text — no formatting at all. Tiny, universal, and works everywhere from a Kindle to a Linux server. The right pick for source code snippets, command lists, and config files.

XLSX

Microsoft Excel's modern format. Use for spreadsheets you'll edit; export to CSV for raw data sharing or PDF for read-only distribution.

CSV

Comma-separated values. The universal data interchange format — every database, spreadsheet, and analysis tool reads it.

Audio formats

MP3

The classic. Lossy compression, small files, plays on literally everything. Best for podcasts, audiobooks, and music sharing. 192 kbps is the everyday quality target; 320 kbps for archival.

WAV

Uncompressed, studio-quality audio. Massive file sizes. Use only for editing or archival.

AAC / M4A

Apple's MP3 successor — better quality at the same size. Default for iTunes and Apple Music. Compatibility is universal in 2026.

FLAC

Lossless audio — every bit of the original preserved. Big files, audiophile choice. Most consumer apps now support it.

Video formats

MP4 (H.264)

The web video standard. Plays everywhere, balances quality and file size beautifully. Default for almost every camera, phone, and editing tool.

MOV

Apple's QuickTime format. Slightly higher quality, larger files. Convert to MP4 for cross-platform sharing.

WebM

Open-source web video. Smaller than MP4 at the same quality, but not all editors support it.

GIF

Old, capped at 256 colors, with terrible compression. Only still useful for short looping clips. For longer or higher-quality video, use MP4 or WebM.

Archive formats

ZIP

Universal compressed folder. Built into Windows, macOS, and every phone. Use this when in doubt.

RAR / 7Z

Better compression than ZIP, but the recipient needs a separate app to open them. Avoid unless you know they have it.

TAR.GZ

The Linux/Unix standard. Common for source code distributions; most modern Macs and Windows installs have built-in support now.

Quick decision cheat sheet

• Photo for the web? WebP (or JPG as a safe fallback)
• Logo or icon? SVG (or PNG)
• Document to share? PDF
• Document to edit? DOCX
• Spreadsheet to edit? XLSX
• Raw data to share? CSV
• Music or podcast? MP3
• High-fidelity audio? FLAC
• Video? MP4
• Bundle of files? ZIP

One last principle

Keep your originals in the highest-fidelity format you have — RAW for photos, WAV for audio, ProRes for video — and only convert to a smaller, lossier format when you ship. Every lossy save loses a little quality, and once it's gone you can't get it back.

Need to switch between any of these? onlinefileconverter handles them all — instantly, in your browser, with zero uploads.

Keep learning

If you found this useful, a few related guides go deeper on adjacent problems: our file-format reference covers when to pick which format, why file conversion matters in 2026 puts the bigger picture together, and why browser-based conversion is safer covers the privacy architecture every tool on this site is built around. For everyday image work, the image resizer and full converter index are the two pages most readers bookmark.

About this guide

This article is part of the OnlineFileConverter editorial library — practical, vendor-neutral writing on file formats, conversion workflows, and digital privacy. Every recommendation here is something we'd give a friend, not a sponsored placement. Our editorial standards page covers how we update articles, who writes them, and how we handle advertising. If you spot something out of date or want a guide on a topic we haven't covered, tell us — we read every note.

Related converters you can try right now

The three tools below are the ones most readers of this guide reach for next. All free, all browser-based, no signup.

• PNG to WebP converter — Modern transparent format, much smaller than PNG.
• JPG to WebP converter — Smaller photos with no visible quality drop.
• HEIC to JPG converter — Make iPhone photos universally compatible.