How log-based measurement works
Overview
Log-based measurement offers an alternative to pixels, with many benefits stemming from the technological differences between pixels and logs. Impression logs (also called exposure logs) can work without third-party (3P) cookies. This quality makes them very valuable in situations where using pixels and collecting 3P cookies is not permitted (e.g. for privacy reasons) or not feasible (e.g. CTV campaigns, mobile campaigns). With the steady decline of 3P cookies worldwide, log-based measurement is a great alternative to pixel-based measurement.
Because impression logs (also called exposure logs) are collected on the server, they are more detailed than the data collected by pixels. The exact format of the data varies between systems, but usually what is collected is impression timestamp, user information, device information, campaign name/id, creative name/id, order and line item details and where the impression took place (geo data).
Should I use Pixels or Logs?
In July 2024 Google reversed its course on the phase-out of third-party cookies. 3P cookies will stay with us in the long term, but they will not be a do-all-end-all technology for campaign measurement and attribution, as users worldwide continue to disable them in their browsers. Logs and pixels used in combination will provide the most comprehensive measurement results. Here is why:
| Logs | Pixels | |
|---|---|---|
| What kind of media can I measure? | Any type of campaign - including CTV and mobile - where the platform supports the export of impression log data | Campaigns that are executed in desktop and mobile browsers, where the creative can be tagged with a pixel. This excludes most native apps, CTV, mobile apps or social media. |
| Will measurement work with privacy-enhanced browsers? | Yes Log data does not rely on third-party cookies from the user’s browser, and impressions are attributable even when the user enabled the browser’s privacy features | No If the user enabled the browser’s privacy features, the impression data will not be usable. |
| Can I retroactively measure campaigns already running? | Yes Most platforms offer at least 30 days of past campaign data | No |
| How fast can I see the reports | Reports take a few days to generate after the impression occurs | Impressions are usually reported within 24 hours |
| What is the setup process? | There is a one-time setup activity per vendor, after which reporting is automatic | Ongoing work is required to place pixels on every campaign |