urlencoder.org has a browser-only live mode, but its standard encoding sends your data to its servers, which it then deletes after processing. A browser-based URL encoder and decoder always runs on your own device, so the text you encode is never transmitted at all.
urlencoder.org is a solid encoder, and to its credit it offers a live-typing option that encodes in the browser without sending anything. Its standard encoding path, though, sends your data to its servers to process, which is why its own copy talks about deleting uploaded files after processing. A tool that always encodes locally removes that path entirely: percent-encoding and decoding are simple text transforms that never need to leave the page.
Always-local encoding matters when the string you are encoding is a query with an API key, a token, or any private value, because it should never be sent to a third party just to be escaped. A client-side encoder and decoder handles the whole job on your device, works offline once loaded, and has no account and no ads.
No. Encoding and decoding run entirely in your browser and are never transmitted.
Yes. It both percent-encodes strings and decodes existing encoded strings back to plain text.
Yes. Once the page has loaded, it works with no network connection.