The Complete Guide to Image Format Conversion (PNG, JPG, WebP, GIF)

LokalTools Image Converter converts between PNG, JPG, WebP, GIF, and other common formats entirely in your browser using WebAssembly and the Canvas API — no file upload, no account, and no software required. It supports batch conversion, preserves transparency where the target format allows, and runs locally on Chrome, Firefox, Safari, and Edge.

You've just exported a graphic from Figma as a PNG and the client's CMS only accepts JPEG. Or you need to convert PNG to JPG to cut file size before emailing a batch of product photos. Or you've received a WebP image that won't open in a legacy application.

These situations come up constantly. Understanding which format to use — and how to convert between them — is a practical skill that saves time and prevents quality mistakes.

Why So Many Image Formats Exist

Each image format is an engineering trade-off between three competing goals: file size, visual quality, and feature support (things like transparency, animation, and color depth). No single format wins on every axis, which is why several coexist in common use.

The formats you'll encounter most often:

Format	Compression	Transparency	Animation	Best for
JPEG/JPG	Lossy	No	No	Photos, gradients
PNG	Lossless	Yes	No (APNG: yes)	Graphics, screenshots, logos
WebP	Lossy or lossless	Yes	Yes	Web images (modern browsers)
GIF	Lossless (limited)	Yes (1-bit)	Yes	Simple animations, memes
AVIF	Lossy or lossless	Yes	Yes	Next-gen web images
BMP	Uncompressed	No	No	Legacy Windows apps
TIFF	Lossless	Yes	No	Print, archiving

An image type converter that handles the common formats lets you move between any of these depending on what the destination requires.

JPEG: The Universal Photo Format

JPEG (Joint Photographic Experts Group) has been the dominant photo format since the 1990s. Its lossy compression works by discarding information the human visual system is least sensitive to — high-frequency detail and color subtlety in areas of complex texture.

For photographic images — portraits, landscapes, product photos, anything with smooth gradients and organic variation — JPEG is nearly always the right choice. At 80–85% quality, JPEG files are small enough for web use, and the compression artifacts are invisible at normal viewing sizes.

Where JPEG fails:

Text and line art: JPEG's block-based compression creates visible artifacts ("ringing") around high-contrast edges. A screenshot of a terminal or a logo saved as JPEG looks noticeably worse than the same image as PNG.
Transparency: JPEG has no alpha channel. Elements that should be transparent (like a logo over a background) will have a solid fill instead.
Repeated re-saves: Each time you open and re-save a JPEG, it re-compresses. Three or four generations of re-saves can visibly degrade quality. Keep a lossless master copy (PNG or TIFF) and export JPEG fresh each time.

PNG: Lossless Quality and Transparency

PNG (Portable Network Graphics) stores every pixel exactly — there is no quality setting and no compression artifacts. This makes it the right format for:

Logos, icons, and graphics with flat colors
Screenshots of text, code, or UI
Images that need a transparent background
Source files you'll edit and re-export repeatedly

The trade-off is file size. A photographic image saved as PNG is typically 3–5× larger than the same image as an 80% JPEG. For web use, this matters for page load time. For archives and working files, PNG's lossless fidelity is often worth the storage cost.

When you convert PNG to JPG, you're accepting some quality loss in exchange for significantly smaller files. The right scenario for this conversion: you have a photo that was mistakenly exported as PNG, or you're preparing a batch of images for a web gallery where page speed matters.

When you convert JPG to PNG, you're not recovering quality lost during the original JPEG compression — you're just re-wrapping the same pixel data in a lossless container. This is useful when you need transparency, or when you're taking a JPEG into an editing workflow and want to avoid additional generation loss from repeated re-saves.

WebP: The Modern Web Standard

Google's WebP format offers lossy compression comparable to JPEG but at roughly 25–35% smaller file sizes for equivalent visual quality. Its lossless mode produces files about 25% smaller than equivalent PNGs. It also supports transparency and animation.

All modern browsers — Chrome, Firefox, Safari (since 2020), Edge — support WebP natively. For any website you control, serving images as WebP instead of JPEG meaningfully improves page load times and Core Web Vitals scores.

The practical limitation of WebP is older software. Some image editing applications, legacy CMS platforms, and email clients still don't handle WebP reliably. If you're sending an image to someone whose software is unknown, JPEG or PNG remains the safer choice.

When to convert to WebP: you're optimizing images for a website and need the best size-to-quality ratio. When to convert from WebP: you've received a WebP file and need to share it with someone whose software doesn't support it.

GIF: Animation and Legacy Uses

GIF (Graphics Interchange Format) predates the web itself, dating to 1987. Its color space is limited to 256 colors per frame, which makes it terrible for photographic images but acceptable for simple graphics and line art. Its animation support is the reason it survived this long.

GIF is almost always the wrong choice for static images in 2025. For graphics, PNG is lossless and supports more colors. For photos, JPEG is far smaller. The only genuinely compelling use case for GIF is short animated loops for contexts that don't support video — some email clients, certain older social platforms.

For new animated content, WebP animation or short MP4 video clips are technically superior in every dimension. But if the output must be a GIF (for a specific platform or tool), an image type converter can export it from video frames or image sequences.

How Browser-Based Conversion Works

Image format conversion in a browser uses the same HTML Canvas API that powers browser-based resizing. The conversion pipeline:

The source image (any format the browser can decode) is loaded and drawn onto a canvas
The canvas is exported in the target format using canvas.toBlob() or canvas.toDataURL()
The browser's built-in codec handles the encoding
The output file is prepared for download

For formats the browser natively supports for both input and output (JPEG, PNG, WebP), this is fully lossless in the decode-to-canvas step and fully controlled in the encode step. For formats like GIF, specialized JavaScript libraries handle the encode since browsers don't support GIF as a canvas output format.

This entire process happens locally. Nothing leaves your device. Use LokalTools Image Converter to convert between formats directly in your browser — no install, no upload. It is, from a privacy standpoint, equivalent to using offline software.

When Conversion Changes More Than the Format

A few conversion scenarios carry important caveats:

PNG with transparency → JPEG: JPEG has no alpha channel. The conversion has to fill the transparent areas with something — usually white or black, depending on the tool. Make sure the background fill matches your intended output context. Some tools let you choose the fill color.

JPEG → PNG: You're not recovering detail lost during the original JPEG compression. The lossless container wraps the same lossy pixel data. What you gain is transparency support and protection from future re-compression — not improved quality from the original encode.

Photographic PNG → JPEG: This is usually the right move when you need to send a photo-realistic image and file size matters. Just remember that the original PNG was lossless, so the first JPEG save is the only generation of quality loss. Keep the PNG master if you might need to re-export.

Lossy to lossless (JPEG/WebP lossy → PNG): The output is lossless, but the image already contains JPEG compression artifacts. Saving as PNG preserves those artifacts exactly — it doesn't undo them.

Try it at LokalTools Image Converter — no upload required.

Frequently Asked Questions

What is the best image format for websites? WebP at 80% quality offers the best size-to-quality ratio for modern browsers. Fall back to JPEG for photographs and PNG for graphics and logos when serving to broader audiences or legacy systems.

How do I convert PNG to JPG without losing quality? PNG is lossless and JPG is lossy — some quality change is unavoidable. Minimize it by exporting at 90–95% JPEG quality. At 80–85%, the result is visually indistinguishable from the original PNG at normal viewing sizes; only pixel-level inspection or extreme zoom will reveal differences.

Does converting JPG to PNG improve quality? No. Converting JPG to PNG does not undo JPEG compression. The lossless PNG container wraps the same pixel data that already contains JPEG artifacts. What you gain is protection from future re-compression and the ability to add transparency.

Why is my PNG so much larger than the JPG of the same image? PNG is lossless — it stores every pixel exactly, with no compression shortcuts. For photographic images (lots of color variation and gradients), JPEG's lossy compression can represent the same visual information in a much smaller file. PNG's size is appropriate for graphics, logos, and screenshots where pixel accuracy matters.

Can I convert a GIF to MP4? Yes. Converting a looping GIF to an MP4 video dramatically reduces file size — typically by 80–95% for long animations — because video codecs like H.264 are far more efficient than GIF's per-frame LZW compression. All modern browsers and social platforms support video playback, making this an almost always correct trade.

What format should I use for a logo? If the logo is vector-based, SVG is the correct choice — it scales to any size without quality loss. For raster logos, PNG is the standard: lossless quality, transparency support, and wide compatibility. Never save a logo as JPEG — the compression artifacts around hard edges are immediately visible against a flat background.

Is WebP supported everywhere? All major modern browsers (Chrome, Firefox, Safari 14+, Edge) and operating systems (Windows 10+, macOS 11+, iOS 14+) support WebP. Legacy software (older versions of Photoshop, certain email clients, some older Windows applications) may not. When the audience is known and modern, WebP is safe. When in doubt, JPEG or PNG remain universally compatible.

How do I keep transparency when converting image formats? Transparency (alpha channel) is supported by PNG, WebP, GIF (1-bit only), AVIF, and TIFF. It is not supported by JPEG or BMP. When converting a transparent image to JPEG, choose a background fill color in the tool. When keeping transparency, convert to PNG or WebP.