How to Convert Image File Formats for Free (Every Format)

The number of image file formats in active use has never been larger. JPEG and PNG remain the dominant web formats, but Google WebP now accounts for over 70 percent of images served on top-1000 websites according to the HTTP Archive 2024 Web Almanac, and AVIF adoption has grown from near zero in 2021 to over 30 percent of new image content on major CDNs. Apple HEIC is the default capture format on every iPhone since iOS 11. Knowing how to convert between these formats quickly and for free is an essential skill for photographers, developers, and everyday users alike.

Understanding the Major Image Formats

JPEG (Joint Photographic Experts Group), also written as JPG, uses lossy compression optimized for photographs. A typical 12-megapixel photo from a modern smartphone is approximately 4 to 8 MB in raw format; JPEG compresses it to 2 to 4 MB with minimal visible quality loss at a quality setting of 80 to 85 percent. PNG (Portable Network Graphics) uses lossless compression and supports full alpha transparency, making it ideal for logos, screenshots, and UI elements. A PNG of the same photo will be 5 to 15 MB.

• JPEG: lossy, best for photos, no transparency, universally supported
• PNG: lossless, supports transparency, best for graphics and screenshots
• WebP: Google format, 25 to 35 percent smaller than JPEG at equal quality, supports transparency
• AVIF: AV1-based, 50 percent smaller than JPEG, best current format, growing browser support
• HEIC: Apple format, 2x smaller than JPEG, not supported by Windows or most browsers without conversion
• SVG: vector format, infinitely scalable, best for icons and logos, not suitable for photos

Free Browser-Based Conversion Tools

For one-off conversions without installing software, three tools stand out. Squoosh (squoosh.app) is a Google open-source web app that converts between JPEG, PNG, WebP, AVIF, and more while letting you preview the exact quality-to-file-size tradeoff in real time. It processes files entirely in your browser — nothing is uploaded to a server. CloudConvert supports over 200 file formats including all major image types and offers 25 free conversions per day. ILoveIMG specializes in bulk image conversion and supports up to 150 images per batch in the free tier.

Converting HEIC Files from iPhone

iPhones running iOS 11 and later save photos in HEIC by default because it is approximately twice as efficient as JPEG. However, HEIC is not natively supported on Windows 10 or 11 without a paid codec from the Microsoft Store, and most web platforms reject HEIC uploads. The simplest conversion method is to change your iPhone capture setting to JPEG: go to Settings, then Camera, then Formats, then select Most Compatible. Existing HEIC files can be converted using the Windows Photos app (right-click, open with Photos, then save as JPG), iMazing HEIC Converter (free desktop app), or any of the browser tools listed above.

Command-Line Conversion with FFmpeg and ImageMagick

For bulk conversions and automation, two free command-line tools handle every format. FFmpeg, primarily known for video, converts image sequences and handles WebP and AVIF natively. ImageMagick is the definitive image processing tool: the command "magick input.jpg -quality 85 output.webp" converts a JPEG to WebP at quality 85. To batch-convert all JPEG files in a folder to WebP on Linux or macOS: "for f in *.jpg; do magick "$f" "${f%.jpg}.webp"; done". ImageMagick supports over 200 image formats and is available free for Windows, macOS, and Linux.

• ImageMagick install: free at imagemagick.org, available via Homebrew on macOS
• Single file: magick photo.jpg -quality 85 photo.webp
• Batch to WebP: for f in *.jpg; do magick "$f" "${f%.jpg}.webp"; done
• Resize and convert: magick input.jpg -resize 1200x800 -quality 90 output.jpg
• Strip metadata for web: magick input.jpg -strip output.jpg (reduces file size 5 to 15 percent)

Conclusion

For one-off conversions, Squoosh at squoosh.app is the best free browser-based tool — it is private, instant, and supports AVIF, WebP, JPEG, PNG, and more. For bulk conversion, ImageMagick is the professional standard used by major web platforms. When shooting with an iPhone, switching your camera setting to Most Compatible eliminates HEIC compatibility problems at the source. As AVIF adoption grows — now at 30 percent of major CDN content — converting older JPEG image libraries to AVIF can reduce storage and bandwidth costs by up to 50 percent with no visible quality loss.