Image Formats Explained: JPEG, PNG, WebP, HEIC and Which Conversions Are Safe

An iPhone shoots HEIC that Windows can’t open. A designer sends a TIFF that won’t upload to the CMS. A logo arrives as a JPG with a white box where transparency should be. An old site has 900 PNGs that should be WebP. Converting between image formats is routine, but each format was designed for a different job, and converting in the wrong direction quietly destroys quality or transparency. This guide is the decision table: what each format is for, which conversions are safe, which are lossy, and how to do them in bulk without uploading anything.

The formats

Format	Compression	Transparency	Animation	Best for
JPEG	Lossy	No	No	Photographs
PNG	Lossless	Yes	No (APNG rare)	Screenshots, logos, graphics with transparency
WebP	Both	Yes	Yes	Almost everything on the web
AVIF	Both	Yes	Yes	Web, where support is confirmed; smallest files
GIF	Lossless, 256 colours	1-bit	Yes	Legacy animations; replace with WebP or video
HEIC/HEIF	Lossy	Yes	Yes	Apple camera default; poor support elsewhere
TIFF	Lossless or none	Yes	No	Print, archiving, scanning
BMP	None	No	No	Nothing modern; convert away from it
SVG	Vector (text)	Yes	Yes (CSS/SMIL)	Logos, icons, diagrams

Safe conversions and lossy ones

Safe (no quality loss): PNG → WebP lossless, TIFF → PNG, BMP → PNG, HEIC → PNG (decodes once, then lossless), any raster → PNG.

Lossy but usually fine: JPEG → WebP lossy at quality 80+ (re-compresses, but WebP is efficient enough that the result is often smaller and looks identical), PNG photo → JPEG or WebP lossy (PNG was the wrong format for a photo anyway), HEIC → JPEG.

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Lossy and destructive:

• Anything with transparency → JPEG. The transparent area becomes white (or black). The Image Converter warns before doing this; choose WebP or PNG instead.
• JPEG → JPEG repeatedly. Each save re-compresses. Ten rounds of editing and saving a JPEG visibly degrade it. Edit from the original or a PNG master, export JPEG once.
• Screenshot or text → lossy anything at low quality. Compression artefacts around letters look terrible. Keep text-heavy images lossless or at quality 90+.
• Any raster → SVG. “Converting” a JPG to SVG wraps the bitmap in an SVG container; it does not become vector. True vectorisation (tracing) is a separate, imperfect process that works for simple logos and fails for photos.
• Colour photo → GIF. 256 colours; banding everywhere. Use WebP or a short MP4 for animation.

The three conversions people actually need

HEIC → JPEG or PNG

iPhones save HEIC by default. Windows needs an extension to open it, many web forms reject it, and older software has never heard of it. Convert to JPEG for photos going anywhere outside Apple, or PNG if you’ll edit them. Alternatively, on the iPhone: Settings → Camera → Formats → Most Compatible, which shoots JPEG going forward.

PNG/JPEG → WebP

WebP is supported by every current browser and is typically 25–35% smaller than JPEG and far smaller than PNG for photos, with transparency support. Convert your web images and the page gets lighter with no visible change. Keep the originals as masters; WebP is a delivery format. For a whole media library, run the Bulk Image Compressor with WebP output, or use a WordPress plugin that serves WebP alongside the originals.

JPEG with a white background → transparent PNG

This isn’t a format conversion; it’s background removal. Converting the JPEG to PNG gives you a PNG with a white background. Run it through the Background Remover first, then it exports as a transparent PNG or WebP.

Colour space and metadata

Two things a conversion can silently change:

• Colour profile. Photos from cameras may be in Adobe RGB or Display P3; the web assumes sRGB. A converter that strips the profile without converting to sRGB makes colours look flat. Good tools convert to sRGB on export for web formats.
• EXIF metadata. Camera model, date, and often GPS location are embedded in JPEG and HEIC. Some converters keep it, some strip it. Stripping is usually what you want for anything published (privacy, and it saves a few KB); keeping it matters for archiving. Check the option.

Frequently asked questions

Which is better, PNG or JPEG?

JPEG for photos (much smaller), PNG for anything with sharp edges or transparency. WebP is usually better than both for web use.

Does converting JPEG to PNG improve quality?

No. The compression damage already in the JPEG stays; you just get a bigger file. PNG only prevents further loss.

How do I open a HEIC file on Windows?

Install the HEIF Image Extensions from the Microsoft Store, or convert the file to JPEG with an online converter that runs in the browser.

Is WebP safe to use on my website?

Yes. Chrome, Safari, Firefox and Edge all support it. Email clients and some older CMS image processors don’t, so keep JPEG/PNG for email.