Overview
Meta requires every conversion you want to optimize for to be defined as a custom conversion in Events Manager, and every remarketing segment to be defined as a website custom audience. On a complex site with a dozen events, that's a lot of manual clicking. AutoTag replaces the clicking with API calls: you provide credentials once, pick a project template, and AutoTag creates both sets of objects in Meta for you.
The critical detail is authentication. Meta's Marketing API accepts several token types, but only System User tokens are durable enough to serve an automation tool. Graph API Explorer tokens expire in an hour or two, and OAuth Standard Access tokens don't have the right scopes to create custom conversions on client accounts. Get the token type right up front and the rest of the setup is straightforward.
Get a System User token
Open Meta Business Manager and navigate to Business Settings > System Users. Create a new System User (or reuse an existing one) and grant it Admin access on the Business. System Users are non-human identities scoped to a Business Manager, which is why their tokens persist indefinitely rather than expiring on the normal OAuth cadence.
Once the System User exists, generate a token for it with the ads_management and ads_read permissions. Copy the token somewhere safe immediately. Meta only shows it once, and generating a replacement takes the original out of service.
Enter credentials
In AutoTag, paste the Pixel ID and System User access token into the platform edit form. The Pixel ID is in Meta's Events Manager under Data Sources. It's a numeric string, not the friendly name. Double-check you're pulling the ID for the pixel that lives in the same Business Manager as the System User, because tokens are scoped to their Business and can't see pixels owned by a different one.
If the pixel is actually owned by a client's Business Manager rather than yours, you'll need the client to create a System User in their Business and provide you with that token. Agency Business Managers can't issue working tokens for pixels they don't own.
Test the connection
Click Test Connection. AutoTag calls Meta to confirm the token has the required permissions and can access the specified Pixel ID. A failed test usually means one of three things: the token is expired or was revoked, the token doesn't have ads_management in its scope list, or the pixel is in a different Business than the System User.
Don't skip this step. A bad token produces a half-written sync where some calls succeed and some don't, and cleaning up partial audiences in Meta is much more painful than fixing a credential and re-running.
Sync custom conversions
Click Sync Conversions. AutoTag iterates over the conversion events for your project type and creates a matching custom conversion in Meta for each. Custom conversions combine a URL rule with an event type filter, which is why AutoTag's project templates carry the right metadata to feed this API.
Meta soft-deletes custom conversions, so ones you previously deleted may still appear in API responses. AutoTag filters these out of the UI but leaves them in place on Meta's side. That behavior is expected; don't treat a name collision on a soft-deleted conversion as a bug.
Sync custom audiences
Click Sync Audiences. AutoTag creates website custom audiences scoped to pixel events, which you can then use in Meta Ads Manager for retargeting. Each audience gets a retention window, and Meta will occasionally return a warning if the retention you requested isn't allowed in a particular region or account state.
AutoTag treats retention warnings as non-fatal. The audience is still created; the warning is surfaced in the sync result panel so you can adjust in Meta if you care. A failed audience sync, on the other hand, is surfaced as an error and should be investigated.
Always use System User tokens for anything beyond experimentation. Graph API Explorer tokens expire in 1-2 hours and OAuth Standard Access tokens can't create custom conversions on client accounts. Meta soft-deletes custom conversions and audiences, so archived items may linger in API responses but are filtered out of the AutoTag UI.
Troubleshooting
Test Connection fails with "Invalid OAuth access token"
The token is either expired, revoked, or was never a System User token in the first place. Regenerate it in Business Settings > System Users, confirm the ads_management and ads_read permissions are selected, and paste the new value into AutoTag. If someone rotated the System User's credentials recently, all old tokens are invalidated at the same moment.
Sync fails on the first custom conversion with a permissions error
The System User has access to the Business but not to the Ad Account tied to the pixel. Open the Business, find the System User, and grant it access to the specific Ad Account. Partner-managed accounts may also need a separate permission grant from the client Business before your System User can write to them.
Audiences created but don't appear in Ads Manager
New website custom audiences take a few minutes to populate and appear in the UI. If more than an hour has passed and the audience is still missing, confirm you're looking at the Ad Account tied to the pixel, not a sibling account in the same Business.