Abstract: The systems and methods are directed to identity resolution service (IRS) which may be used to enable accurate and faster conversion contribution analysis across multiple channels. IRS may be responsible for keeping track of relationships between user identifiers and for determining a user canonical identifier given a set of input identifiers and identity mappings. Users may utilize multiple devices and browsers to view advertisements and perform actions that result in conversion events. Users may be anonymous on one device but logged in and recognized on a different device and/or browser. The canonical identifier associated with a user may be used to obtain a full set of conversion events generated by the user and the full set of ad traffic to which the user was exposed. Conversion attribution analysis using the full set of conversion events and full set of ad traffic will result in accurate conversion rates for advertisers.