Can I change a file format by renaming the extension?

No. The extension is only a label; the data inside stays in the old format. Renaming photo.heic to photo.jpg produces a file that many programs will refuse to open, because the bytes are still HEIC. The only rename that is safe is between two names for the same format, like .jpg and .jpeg. To really change the format, the file has to be converted — decoded and re-encoded by a tool that understands both formats.

How do I change a photo from HEIC to JPG?

Use a converter that decodes HEIC and re-encodes it as JPG. A browser-based HEIC to JPG converter does this locally in seconds: drop the photo in, set the quality, download the JPG. On a Mac, Preview’s File → Export also works; on Windows, most versions need either a converter or the paid HEVC extension.

Does converting a file reduce its quality?

It depends on the target format. Converting into a lossless format (PNG, BMP, or a PDF wrapping the original pixels) adds no new loss. Converting into a lossy format (JPG, WebP at typical settings) applies compression — usually invisible at high quality settings, but irreversible. Converting can never restore quality the source already lost, so keep your original file until you are happy with the result.

How do I change a file format without downloading software?

Use an in-browser converter. Modern browsers can decode and re-encode images entirely on your device, so a well-built web converter never uploads the file at all — which is faster and more private than upload-based sites. The LK Forge image and PDF converters work this way: the file stays on your device and there is no sign-up.

Why can’t I see file extensions on my computer?

Both major systems hide them by default. On Windows, open File Explorer and tick View → Show → File name extensions. On a Mac, open Finder → Settings → Advanced and tick “Show all filename extensions.” Turning extensions on is worth doing before any conversion, so you can see what you actually have.

Files & Formats

How to Change a File Format

LK Forge · 5 min read · Updated July 2026

"Changing a file format" really means converting the file — decoding what's inside and re-encoding it in a different format. The single most common mistake is renaming the extension and hoping: that changes the label, not the contents. This guide covers what a format actually is, the three ways to convert properly, and the fastest route for the conversions people need most often.

Format vs. extension — they are not the same thing

A file's format is how its data is arranged inside — the byte layout that makes a PNG a PNG. The extension (.png, .jpg, .docx) is just part of the file name, a hint that tells your operating system which program to open it with. Programs read the bytes, not the name. That's why renaming photo.heic to photo.jpg doesn't make it a JPG: any app that opens it finds HEIC data behind a misleading name, and most will show an error.

The one case where renaming is fine is when two extensions name the same format — .jpg and .jpeg are identical, as are .htm and .html. Everything else needs real conversion.

The three ways to actually change a format

An in-browser converter. For images and simple documents this is the fastest route: the file is decoded and re-encoded by your own browser, on your own device, with nothing uploaded. Drop the file in, pick the target format, download. This is how the LK Forge image converter and PDF converter work.
The app's own "Save As" or "Export". If a program can open the file, check its File menu — Word exports .docx to PDF, Preview on macOS exports HEIC to JPG, image editors export to most image formats. Best when you're already working in that app.
A desktop converter for bulk or exotic formats. Hundreds of files, or audio/video formats (MP4, MKV, WAV, FLAC), call for dedicated software — video especially, since re-encoding is heavy computation. For everything on this page, though, a browser handles it fine.

The most common conversions, solved

You have	You want	Do this
HEIC (iPhone photo)	JPG that opens anywhere	HEIC to JPG converter
WebP (saved from the web)	PNG for editing or uploads	WebP to PNG converter
Heavy PNG screenshot	Small JPG for e-mail	PNG to JPG converter
JPG	Lossless PNG	JPG to PNG converter
PNG for a website	Smaller WebP	PNG to WebP converter
Images, or a Word .docx	One PDF	Image & Word to PDF converter
GIF or BMP	Any modern image format	Image converter (all pairs)

First, make extensions visible

Windows and macOS hide extensions by default, which is how report.pdf.exe scams and double-extension confusion happen. Turn them on before converting anything:

Windows: File Explorer → View → Show → File name extensions.
macOS: Finder → Settings → Advanced → Show all filename extensions.

Two things to know before you convert

Lossy targets discard data permanently. JPG and WebP compress by throwing detail away; PNG and BMP don't. Converting lossy → lossless stops further loss but cannot recover what's gone. Keep the original until you've checked the result.
Conversion can drop metadata. Re-encoding an image through a browser canvas strips EXIF data — camera model, timestamps, GPS location. For sharing photos that's usually a privacy win; for archiving, keep the original alongside the converted copy.

For images, the short version of this whole guide: open the image converter, drop the file in, pick the format, download. The file never leaves your device — which is the way format conversion should work.

Convert HEIC, PNG, JPG, WEBP, GIF and BMP right in your browser — nothing is uploaded, no sign-up.

Open the Image Converter