Browser-based
Your file is processed locally without waiting for a server conversion queue.
No upload required
Files stay in your browser, which is ideal for private drafts and personal libraries.
Free ebook tool
Merge and split ebook files without signup, credits, watermarks, or installation.
How to compress a CBZ file
Upload your comic
Drop a CBZ or ZIP archive into the tool — it opens locally in your browser.
Pick a preset
High quality keeps large pages, E-reader matches 6–8″ screens, Smallest squeezes hardest.
Compress and download
Every page is re-encoded with a no-growth guard: any image that would get bigger stays untouched.
FAQ
Will compression damage my pages?
Presets trade size for quality gradually. The E-reader preset resizes to what a 6–8″ screen can actually show, so the loss is invisible in practice. Any image that would grow after re-encoding is kept byte-for-byte.
Why compress for Send to Kindle?
Amazon's Send to Kindle rejects email deliveries over roughly 50MB. Compressing a large volume under that limit lets you push it straight to your device.
Are my files uploaded?
No. Decoding, re-encoding and repacking all run in your browser — the archive never leaves your device.
What about PNG pages?
PNG is lossless, so it only gets re-encoded when a preset downscales it; otherwise the original bytes are kept.