Free Conva Studio — A layered cover editor with book-title presets, magic eraser and background removal — plus batch PNG to JPG at quality 100 and 4:4:4 chroma. No upload.
PNG to JPG without the quality loss you did not agree to
Most online converters re-encode your image at quality 75 with 4:2:0 chroma and call it lossless. This one does not.
Free Conva Studio converts PNG files to JPG without throwing away anything it does not have to. It encodes at quality 100 with 4:4:4 chroma — full colour resolution, no subsampling — using a real MozJPEG encoder compiled to WebAssembly, not the browser's built-in one, which quietly halves colour detail on every file it touches. The same workspace is also a layered cover editor: multi-page canvas, 14 book-title presets, a content-aware magic eraser, background removal and print-ready PDF export. Everything runs on your own machine. No account, no upload, no server — your images never leave the browser.
What Free Conva Studio does
Quality 100, 4:4:4 chroma
JPEG is a lossy format, but quality 100 with no chroma subsampling keeps full colour resolution and the finest quantisation table libjpeg offers. The result is visually indistinguishable from the source PNG on everything short of extreme gradients.
A real JPEG encoder, in your browser
MozJPEG compiled to WebAssembly. The browser's own canvas.toBlob('image/jpeg') is never used for JPEG output — it silently subsamples chroma to 4:2:0 and there is no way to turn that off.
Batch convert whole folders
Drop in as many files as you like and convert them in one pass, with a quality preset, an optional resize cap, a filename suffix and a matte colour for transparency. Results are written to a folder you choose, or downloaded as a single ZIP.
PNG and WebP stay truly lossless
PNG export is byte-exact — the pixels that go in are the pixels that come out. WebP at Maximum uses true lossless mode rather than quality 100, which is not the same thing.
Print-ready PDF at an exact size
A PDF page is measured in points, so what decides the printed size is pixels ÷ DPI. An 1800 × 2700 px cover at 300 DPI becomes a page of exactly 6.000 × 9.000 in, and the JPEG is embedded untouched — the PDF layer never recompresses it.
Multi-page canvas editor
Layers with 10 blend modes and per-layer opacity, brightness, contrast, saturation and blur adjustments, crop presets for common trim sizes, 17 vector shapes — stars, bursts, banners, polygons and arrows for badges and award strips — plus gradient scrims and vignettes. Undo and redo span the whole document, across page add, delete and reorder.
14 book-title presets
Gold foil, neon, thriller, fantasy, horror, vintage, romance, sci-fi chrome, letterpress, blockbuster and more — each with its own typeface, fill, outline, shadow and 3D extrude. Nine typefaces ship with the tool, so a cover looks the same on every machine.
Rulers and drag-out guides
Rulers run along the top and left of the canvas and stay pinned as you scroll and zoom. Drag from either one to pull out a guide, which snaps to the page edges, the centre and other guides — and every guide applies to all pages at once, so margins and a spine line stay consistent across a whole document. Guides are undoable, saved with your work, and never appear in an export.
Magic eraser and magic wand
Paint over something you want gone and the area is rebuilt from the surrounding image by a PatchMatch content-aware fill running in a Web Worker. Every pixel outside your mask is left byte-identical. The wand knocks out flat backdrops by colour with adjustable tolerance and feathering.
Picks up where you left off
The document — pages, layers, text and the image data itself — is kept in this browser as you work, so navigating away, closing the tab or reloading does not cost you anything. It is restored on your next visit with a one-click option to start fresh instead.
Background removal that stays local
A U²-Net cut-out model runs in the browser through ONNX Runtime Web. The fast model ships with the page; two larger, more accurate ones can be downloaded once and are cached for next time. Your image is never sent anywhere — only the model comes down.
How to convert PNG to JPG with no quality loss
Add your images
Open the Batch Convert tab and drop your PNG files in, or use Choose Files. Each one is measured as it arrives — dimensions, file size, and whether it actually uses transparency rather than merely carrying an alpha channel.
Pick a quality preset
Maximum is the point of the tool: quality 100, 4:4:4, no MozJPEG extensions. Maximum (smaller) keeps the same settings but turns on trellis quantisation for a file typically 15–30% smaller with no visible difference. High is quality 95, Balanced is quality 85 at 4:2:0 for the web.
Set a matte colour if you need one
JPG cannot store transparency. If any of your files actually use it, the tool highlights the matte swatch and tells you how many — those pixels are painted with the colour you choose instead of defaulting to black.
Choose where the results go
On Chrome or Edge, pick an output folder and the files are written straight into it, with an overwrite toggle and automatic (1), (2) suffixes when you leave it off. On Safari and Firefox the results arrive as one ZIP download instead.
Or design a cover in the Editor tab
Start from a blank KDP trim size or open an image, add layers and a title preset, then Export as JPG, PNG, WebP or a print-ready PDF. The export always renders at true document resolution, whatever zoom you happen to be at.
Which output format to pick
| Format | Lossless? | Transparency | Best for |
|---|---|---|---|
| JPG | No — but Maximum is visually identical | No, flattened onto a matte colour | Cover uploads, print submission, anywhere a JPG is required |
| PNG | Yes, byte-exact | Yes | Artwork with transparency, flat colour, text and screenshots |
| WebP | Yes at Maximum | Yes | Web delivery at a smaller size than PNG |
| Matches the embedded image | Yes, with PNG inside | Print-ready output at an exact physical page size |
Frequently asked questions
Does converting PNG to JPG lose quality?
Some loss is unavoidable — JPEG is a lossy format and PNG is not. What is avoidable is everything most converters throw away on top of that. At quality 100 with 4:4:4 chroma the error is far below what any eye can see: measured against the source, the mean channel error is under 1/255. The usual culprits are a default quality around 75 and 4:2:0 chroma subsampling, which discards three quarters of the colour information before the quality setting is even applied.
What is 4:4:4 chroma subsampling, and why does it matter?
JPEG stores brightness and colour separately, because the eye is far more sensitive to brightness. 4:2:0 exploits that by keeping only one colour sample for every four pixels — invisible on photographs, very visible on book covers, logos, screenshots and anything with saturated text against a contrasting background, where it shows up as coloured fringing on edges. 4:4:4 keeps a colour sample for every pixel. This tool sets it explicitly rather than trusting the encoder to choose.
Are my images uploaded anywhere?
No. There is no server, no account and no storage. Decoding, encoding, PDF assembly and background removal all run in your browser through WebAssembly, and your files are read straight off your disk. The only thing ever fetched over the network is the optional background-removal model, and that is weights coming down, never your image going up.
What is the difference between the two Maximum presets?
Both encode at quality 100 with 4:4:4 chroma, so both are visually identical to the source. Maximum produces a plain baseline JPEG with MozJPEG's extensions switched off, which is the most compatible and most conservative option. Maximum (smaller) turns on trellis quantisation and progressive scans, which removes bits the eye cannot see rather than bits the image needs — typically 15–30% smaller for the same visual quality.
Why is my JPG larger than the PNG it came from?
That is expected at Maximum, and it is the trade the preset exists to make. Quality 100 with no chroma subsampling stores a great deal of detail, and for flat artwork, screenshots or images with large areas of a single colour, PNG's lossless compression is simply better suited. If size matters more than absolute fidelity, Maximum (smaller) or High will be dramatically smaller and still look the same.
How many files can I convert at once?
There is no fixed limit when you pick an output folder — files are written one at a time as they finish. If your browser cannot write to a folder, the results have to be held in memory until the ZIP is built, so the tool warns you past roughly 50 files or 500 MB and lets you decide whether to continue or split the batch.
Which browsers can write straight to a folder?
Chrome, Edge and other Chromium browsers, through the File System Access API. Safari and Firefox do not implement it, so they get a ZIP download and an anchor-based Save instead. The tool feature-detects this rather than checking the browser name, and hides the controls that would not work.
What size should a book cover be for Kindle or print?
For KDP print, work at 300 DPI: a 6 × 9 in trim is 1800 × 2700 px, 5 × 8 in is 1500 × 2400 px, and 5.5 × 8.5 in is 1650 × 2550 px. A Kindle ebook cover is 1600 × 2560 px, and an audiobook cover is square at 3000 × 3000 px. All of these are in the New Cover dialog, and the crop tool has matching ratio presets.
Is EXIF and colour-profile data preserved?
No. The browser encoders write a clean file, so EXIF, orientation tags and embedded ICC profiles are dropped. Pixel data is carried over exactly. If you need an embedded profile to survive, convert with a desktop tool instead — this is a genuine limitation of doing the work client-side, and the panel says so rather than pretending otherwise.
Can I open TIFF files?
No — browsers cannot decode TIFF, so there is nothing the tool can do about it without shipping another decoder. PNG, JPG, WebP, GIF, BMP and AVIF all work. Convert a TIFF to PNG first and nothing is lost on the way in.
Does it work on a phone?
It loads, but it is built for a full-size screen and will tell you so on a small one. iOS Safari enforces a hard cap on canvas area and discards backgrounded canvases aggressively, so print-resolution artwork at 1800 × 2700 px and up can fail there in ways that look like bugs. Batch conversion of smaller files is generally fine.
Does my work save automatically?
Yes. The whole document — every page, layer and text setting, plus the image data — is written to this browser's storage as you work, and restored when you come back. It stays on your device; nothing is synced to an account, so it will not follow you to another browser or machine. When a session is restored the tool says so and offers a one-click way to start fresh, and starting a new cover replaces the saved copy.
Is it really free?
Yes — free to use, with no account, no sign-up, no watermark, no export limit and no paid tier. It is a browser page: there is no per-user cost to us because there is no server doing the work.
Other free tools
Cover Designer
A simpler, guided book-cover maker — pick a genre style, set your title and author, export a PNG or JPG. Start here if you want a cover rather than a canvas.
EPUB Studio
Turn a manuscript into a KDP-ready EPUB 3 ebook — chapters, live Kindle-style preview, typography and a cover, exported straight from your browser.