Relabely is a free web tool that takes a shipping label printed on an 8.5 by 11 or A4 sheet and turns it into a 4 by 6 page that a thermal label printer can use without scaling.
It exists because the two formats do not match. Marketplaces generate labels as full size document pages, because that is what an ordinary office printer expects. Thermal printers want a page that is exactly 4 by 6. Send one to the other and the label either shrinks until the barcode stops scanning, or gets cropped in half.
It was written for a working reselling operation, not as a demonstration. The person who built it was printing labels from several marketplaces every day and wasting label stock on scaled and sideways prints.
Because of that, the tool was developed against real label files rather than invented ones. It was built and tested using actual PDFs from eBay, StockX, GOAT and Vinted, which is how it came to handle the awkward cases: labels that arrive encrypted, labels printed upside down on their page, and pages that carry a shipping label and a packing slip together and need to become two separate labels.
A shipping label carries a customer's full name and street address. Sending that to a stranger's server in order to crop a rectangle is a poor trade, and it is not necessary. Modern browsers can read and rewrite a PDF perfectly well on their own.
So Relabely does the whole job on your device. There is no server that receives your files, no account, and no history. The privacy notice sets out what that means in detail, and what the hosting and advertising on the site do collect.
The site is paid for by the advertising on the page. There is no paid tier, no upload limit, and no watermark, and there are no plans to add any.
Ads are kept out of the working area of the tool, and every ad space reserves its height before it loads so the page does not jump while you are using it.
If a label format comes out wrong, that is worth reporting, because the fix is usually to test against a real file of that type. See the contact page.