What the Reddit Conversions API is
The Reddit Conversions API (often shortened to Reddit CAPI) is Reddit's server-to-server route for conversion events. Your server sends an event such as a purchase straight to Reddit's ads API, authenticated with an access token you generate in Reddit Ads Manager next to your pixel id.
It's meant to run alongside the Reddit Pixel, not replace it. The pixel sees what happens in the browser; the Conversions API makes sure the purchase still reaches Reddit when the browser didn't send it.
Reddit's own Shopify app, and where server-side fits
Reddit has its own Shopify app, Reddit Ads (free to install, listed on the Shopify App Store since March 2026, checked October 2026). It connects your store to Reddit Ads, syncs your product catalog for Dynamic Product Ads and sets up the Reddit Pixel without code. Its listing doesn't mention the Conversions API.
That makes it a good starting point for catalog and pixel. If Reddit is a real ad channel for you, the open question is whether purchases from Reddit clicks reach Reddit when the browser blocks the pixel. That's the gap a server-side Conversions API setup closes, and the two can run side by side as long as they share a conversion id (see below).
Why Reddit sales go missing in the browser
Ad blockers and privacy browsers that block tracking scripts by default are common among people who spend time on Reddit. When the Reddit Pixel is blocked, the purchase never leaves the browser, however well the pixel is installed.
A lot of Reddit browsing also happens in the Reddit app. Someone taps your ad, looks around in the in-app browser, and comes back later in Safari or Chrome to buy. Without the click saved on your side, the purchase in the second browser has no link to the ad.
What Reddit uses to match a purchase
- rdt_cid: Reddit's click id, added to your landing URL when someone clicks your ad. Saved at landing, it ties the sale to that click.
- The browser id the Reddit Pixel stores in the _rdt_uuid cookie.
- Email and phone, hashed with SHA-256. Settl lowercases the email and normalizes it the way Reddit asks before hashing.
- IP address and user agent from the visit.
- Order value, currency, the products and a conversion id.
Deduplication: one conversion id on both routes
If the Reddit Pixel and the Conversions API both report the same purchase, Reddit needs a way to see they're one sale. That's the conversion id. The pixel and the server must send the same id for the same order and event, or Reddit Ads Manager will show more purchases than you had.
Settl generates one id per action and sends it on both routes: as conversionId on the pixel and as conversion_id on the server event. If your pixel comes from Reddit's app and server events come from another tool, check that the ids match before you trust the totals.
How to check it in Reddit Ads Manager
In Reddit Ads Manager, open Events Manager and your pixel. Recent events show up there with their source, and the event testing view lets you follow a test order through. Place one and confirm the purchase arrives with the right value and currency.
Then compare a week of Reddit purchases with your Shopify orders that came from Reddit ads. If the gap stays large after adding server events, the click id is usually not reaching your store: check the ad's destination URL and its parameters. Settl's hourly tracking health check flags ad visits that arrive with an empty or template click id, per platform, so you can fix the link.
Common mistakes
- Sending the purchase from two sources with different conversion ids.
- Reading rdt_cid at checkout instead of at landing, after the buyer has already switched browsers.
- Sending events without value and currency, so Reddit can't optimize for revenue.
- Cutting Reddit on pixel numbers alone when the pixel was blocked for a big part of the audience.