What is Seznam Event Measurement (SEM)
SEM is Seznam's new measurement standard (2026 rollout). A single sul.js script replaces the old separate retargeting (rc.js) and conversion codes and supports server-to-server (S2S) measurement via sem.seznam.cz.
1. Deploy sul.js
sul.js must run on every page — it sets the first-party cookies sid and udid that Seznam uses to match user identity. Without them an S2S conversion can't be attributed correctly.
2. Get the separate SEM ID for S2S
In the Sklik UI under SEM measurement you'll find a separate SEM ID for server-to-server (distinct from the base script). No access token — identification runs via the SEM ID + the sid/udid cookies that sul.js sets.
3. Fill it in in DataNostro
Dashboard → Platforms → Sklik (SEM) — enter the SEM ID. DataNostro then reads sid/udid on the server, hashes personal data with SHA-256 and sends events to sem.seznam.cz/rtgconv (asynchronously, with a 3–5 s timeout).
4. Consent
SEM respects consent via IAB TCF or Google Consent Mode. DataNostro passes the consent state through, so only consented events are measured.
5. Test it
SEM conversions in Sklik usually appear within 24 hours. For faster debugging use the SEM debugger and route test traffic to a specific campaign.