## Problem and Background
All pixels, when fired, have a cookie2 value which is in a recognized format. The value should start as `
uid=` and contain `
:ts=` and `
:hc=` parameters. If not, then it is flagged as an error.
cookie2` is used for tracking analytics across products and is needed for any personalization feature.
cookie` is a legacy cookie used as a fallback if `
cookie2` is not present. It has been deprecated and we recommend to stop using it. In case you are using older version of br-trk we recommend updating it.
## Debugging Steps
Use [Pixel Monitor](🔗) to download failure examples. Open General > Pixel Parameters > "Invalid uid in Cookie parameters" check. It will show you actual cookie value and URLs where this happened to help you troubleshoot.
In case you are not able to troubleshoot yourself, request assistance from the [Bloomreach Support](🔗) team.
## Common Causes
This occurs when there are issues with tracking or in the Br-trk tracking code.
Check how you are setting cookie2 values in your pixel tracking requests. If you can't resolve it contact [Bloomreach Support](🔗) for assistance.
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