Reddit ads append rdt_cid to outbound clicks. The destination's Reddit Pixel stores it and attaches it to conversion events sent back through the pixel or Reddit's Conversions API, tying what you do on the site to the promoted post you clicked.
Reddit rolled it out as its ads business grew through 2022 and 2023, on the same first-party pattern as fbclid and ttclid.
Is it safe to remove?
Yes. Attribution-only; pages render identically without it.
Remove rdt_cid automatically
Rather's Link Shortener strips rdt_cid and hundreds of parameters like it, right in the
address bar and in everything you copy or share. Free, open source, no account,
no data collection, and the page you are on never breaks: the cleanup happens
after the site has already loaded.
Reddit's click identifier, appended to ad clicks so the destination site's Reddit Pixel can report your actions back to Reddit for ad attribution.
Is it safe to remove rdt_cid from a URL?
Yes. It is an attribution-only token and pages render identically without it.
How do I remove rdt_cid automatically?
The free, open-source browser extension Rather's Link Shortener removes rdt_cid automatically in the address bar, in copied links, and in shared links, on Chrome and Firefox. You can also simply delete the parameter by hand: everything from rdt_cid= up to the next & or the end of the URL.