OCXLY Tools — Image Formats

JPG to PNG.

Drop in a JPEG, get back a lossless PNG — instantly, free, and entirely inside your browser. Nothing leaves your device.

100 % client-side No upload · No account Batch convert

§ Converter · Free · Private · Instant

Convert JPG files to PNG

Drop one image or a whole batch. Each file is decoded in a canvas element inside your browser and re-exported as a lossless PNG — no quality setting to tune, no watermark, no size limit beyond your device's RAM.

Drop JPG files here, or click to browse

Accepts .jpg & .jpeg — any size, any quantity

Files are processed locally · never uploaded

§ 01 Format Guide

What are these
formats?

A plain-English explanation of what JPG and PNG actually are, where each came from, and when you'd pick one over the other — with sources.

.jpg / .jpeg

JPEG — Joint Photographic Experts Group

JPEG stands for Joint Photographic Experts Group, the ISO/IEC working group that created the standard.[1] The group published the format in 1992; it was formally approved as ISO/IEC 10918-1 in 1994 and simultaneously as ITU-T Recommendation T.81.[2]

JPEG's defining property is lossy compression. It works by dividing an image into 8×8 pixel blocks and applying the Discrete Cosine Transform (DCT), then discarding frequencies the human eye is least sensitive to.[2] The result is dramatically smaller file sizes than uncompressed images, at the cost of some irreversibly lost data — which is why re-saving a JPEG repeatedly degrades it.

JPEG is the dominant format for photographs on the web today,[3] because photos contain complex colour gradients that compress extremely well with DCT. It supports up to 24-bit true colour (16.7 million colours), but has no alpha channel — transparency is not possible.

Lossy compression — some data is permanently lost on save
Excellent for photographs and complex gradients
No transparency support
File extensions: .jpg, .jpeg

.png

PNG — Portable Network Graphics

PNG (pronounced "ping") stands for Portable Network Graphics. It was originally designed as a patent-free replacement for GIF, and the W3C issued the first PNG specification as a Recommendation on 1 October 1996.[4] The format is now standardised as ISO/IEC 15948 and maintained by the W3C PNG Working Group, which published a Third Edition in 2025.[5]

PNG uses lossless compression: every pixel is stored exactly — no data is ever thrown away, regardless of how many times you save the file. Compression is achieved through a combination of filtering (predicting pixel values from neighbours) and the DEFLATE algorithm.[6]

Uniquely among widely-supported web formats, PNG supports a full alpha channel — per-pixel transparency from fully opaque to fully transparent. This makes it the format of choice for logos, icons, UI screenshots, and any image that must be composited onto an arbitrary background.

Lossless compression — no data loss, ever
Full alpha channel (per-pixel transparency)
Best for screenshots, logos, diagrams, UI elements
File extension: .png

When to use which

Use JPEG for photographs destined for the web when file size matters more than pixel-perfect fidelity — a hero image, a product photo, or a social-media thumbnail. The compression artefacts are typically invisible at a quality setting of 80–90.

Use PNG when you need transparency, when the image contains text or sharp-edged graphics (where JPEG's block artefacts become visible), or when you intend to edit and re-save the file multiple times. Each JPEG re-save re-applies lossy compression; a PNG save is lossless, so editing loops don't accumulate artefacts.

Converting JPG → PNG does not recover lost detail — the conversion captures the decoded pixels of the JPEG exactly as they are. The converted PNG will be pixel-identical to what you see in the JPEG viewer, just stored losslessly going forward. This is useful as an intermediate step before editing, or when a workflow requires PNG input.

Sources & further reading

Joint Photographic Experts Group. About JPEG. jpeg.org/jpeg — The committee's own description of the standard's history.
ISO/IEC JTC 1/SC 29/WG 1. ISO/IEC 10918-1: Information technology — Digital compression and coding of continuous-tone still images. 1994. Also published as ITU-T T.81 (September 1992). Cited in ANSI Blog: The JPEG Standard.
MDN Web Docs. Image file type and format guide. Mozilla. developer.mozilla.org — "JPEG: Good choice for lossy compression of still images (currently the most popular)."
World Wide Web Consortium. PNG specification issued as W3C Recommendation (press release, 1 October 1996). w3.org/Graphics/PNG
W3C PNG Working Group. Portable Network Graphics (PNG) Specification (Third Edition). W3C Proposed Recommendation, 2025. w3.org/TR/png-3
Boutell, T. et al. PNG (Portable Network Graphics) Specification Version 1.0. IETF RFC 2083, March 1997. datatracker.ietf.org/doc/html/rfc2083

§ 02 FAQ

Common questions.

01 Does this tool upload my photos anywhere?

No. The conversion happens entirely inside your browser using the HTML Canvas API. Your files are read by FileReader, decoded into a hidden <canvas> element, and exported as PNG blobs using canvas.toBlob("image/png"). Nothing ever leaves your device or touches a server.

02 Will converting a JPG to PNG make the background transparent?

No. Converting only changes the container format and compression method. The pixels — including any background — are preserved exactly as they appear in the JPEG. Adding transparency requires editing the image afterward in a tool such as Photoshop, GIMP, or Figma.

03 Will my converted PNG look better than the original JPG?

It will look identical, not better. PNG is lossless, so it stores every pixel exactly as the JPEG decoded it — without adding new compression artefacts. The converted PNG file will also typically be larger than the source JPEG for photographic content, because PNG's lossless compression does not compact photo data as aggressively as JPEG's DCT-based lossy compression.

04 Is there a limit on how many images I can convert at once?

There is no fixed limit in the tool — you can drop in as many JPEGs as you like and convert them in one batch. The practical ceiling is your device's available RAM, since every image is decoded into a canvas element in memory. Large batches of high-resolution photos (above 20 MP) may slow down on devices with limited memory.

05 Why would I want a lossless PNG instead of just keeping the JPG?

PNG is the better intermediate format when you plan to edit, crop, or re-save an image multiple times. Each JPEG save re-applies lossy compression, accumulating artefacts across generations. PNG saves are lossless, so editing cycles don't degrade quality. PNG is also the expected format for screenshots, diagrams, app icons, and images that mix flat colour with text or sharp edges — where JPEG's block artefacts become visible.

06 Can I convert PNG files back to JPG with this page?

This page is dedicated to JPG → PNG. A PNG → JPG converter following the same in-browser, zero-upload approach will live alongside this one in the OCXLY Tools collection at ocxly.com/tools.