Epsilon, owned by Publicis Groupe since 2019, sells PeopleCloud, a marketing platform built on CORE ID, a person-level identifier tied to name and postal address. Buyers look elsewhere when they want data licensed into their own systems, independent of a media relationship, or when their models need location, CTV or property inputs.
TL;DR
- Pick GSDSI when your team wants smart TV viewing, device linkages, location or consumer attributes as data it stores and models on its own.
- Pick Epsilon when you want recognition, media buying and measurement from one supplier on one identifier, often through a Publicis agency.
- Judge platform and media results apart from the data itself, and test the data on your own file before anyone signs.
Where Epsilon is strong
Epsilon has been assembled over many years. Under its former parent Alliance Data it took on the Abacus cooperative database business in 2007 and the digital media company Conversant in 2014. Publicis Groupe bought Epsilon from Alliance Data and closed the deal in July 2019.
Its identity product is CORE ID. The name comes from the Conversant One-to-One Relationship Engine, and Epsilon describes CORE ID as a deterministic, person-level identifier mapped to a verified name and address rather than to a cookie or a device. Epsilon also sells data on its own: TotalSource Plus, a compiled consumer database with demographic, financial and lifestyle attributes, and Contact Complete, which appends missing contact details and attributes to a customer file. PeopleCloud is the platform built around CORE ID, with a clean room preloaded with Epsilon data and identity, digital and CTV advertising, and a retail media offer for retailers and the brands that sell through them.
That combination pays off for a brand with a large known customer base, heavy loyalty, email or direct mail programs, and a Publicis agency relationship. It gets recognition, media and measurement from one supplier, all keyed to the same person-level ID, and fewer handoffs between vendors.
Sources: Publicis Groupe finalizes the acquisition of Epsilon (2019); Alliance Data Form 10-K for 2007, Abacus acquisition (SEC); Alliance Data announcement on Conversant, 2014 (SEC); AdExchanger on Conversant and CORE; Epsilon CORE ID overview; Epsilon on TotalSource Plus demographic, financial and lifestyle data; Epsilon Contact Complete; Epsilon PeopleCloud Clean Room; IDC MarketScape 2025: Epsilon named a CTV leader; MediaPost on Epsilon Retail Media, formerly CitrusAd
Reasons buyers compare Epsilon with other vendors
The question is usually what you are buying, not whether Epsilon can deliver it.
- Data without a platform commitment. Some teams want attributes or linkages landed in their own warehouse under a license that stands apart from any media or platform agreement, and they compare several suppliers on that basis.
- A different holding company. Brands whose agency belongs to another group sometimes prefer a data source with no competing media arm.
- Raw inputs for an in-house model. Data scientists often want mobile location, POI polygons, smart TV viewing logs or property records they can join and test themselves.
- Device-level linkages. Some teams want mobile ad ID to hashed email pairs they can store, audit and join in their own graph, next to whatever person-level ID they already use.
- Budget sequencing. A paid pilot on one feed clears finance faster than a platform agreement.
Epsilon next to GSDSI
Epsilon entries rely on Epsilon's own pages and the reporting cited in this guide. GSDSI entries rely on our product pages.
| Consideration | Epsilon | GSDSI |
|---|---|---|
| Parent company | Publicis Groupe, since July 2019 | Independent; founded in 2018 and based in Fort Lauderdale |
| Identity approach | CORE ID, a person-level ID anchored to verified name and address | Linkages such as mobile ad ID to hashed email that you hold and join yourself |
| Main offer | PeopleCloud marketing platform and media, plus data products such as TotalSource Plus and Contact Complete | Licensed data feeds scoped to a use case |
| Media buying | Digital, CTV and retail media run through Epsilon | None. GSDSI does not buy or sell media |
| Clean room | Epsilon Clean Room, preloaded with Epsilon data and identity | No hosted clean room; data can be licensed into the one you already use |
| How results reach you | Data appends to your file, or activation and measurement through PeopleCloud | Files or tables sent by S3, SFTP, Snowflake share or API |
Signs GSDSI fits your project
- Your data science team needs smart TV viewing, POI polygons or mobility signals as model features, next to consumer attributes.
- You buy media through several agencies, or in house, and want data that belongs to none of them.
- You want mobile ad ID to hashed email linkages to load into an identity graph you run.
- Retail or CPG analysis where purchase signals and store visits have to meet in one warehouse.
Signs Epsilon fits better
If most of these describe your situation, keep Epsilon on the short list.
- You want recognition, media buying and measurement from one supplier on one identifier.
- Your agency is part of Publicis Groupe and already works in PeopleCloud.
- You are a retailer building a retail media business and want a platform partner for it.
- You need someone to run the campaigns. GSDSI does not run media, send email or operate loyalty programs, so we are no substitute for those services.
Other Epsilon alternatives
Choose by the piece of Epsilon you want to replace.
- Acxiom: Omnicom's data and identity company, built around InfoBase and Real ID. Compared on its own page.
- Unified ID 2.0: an open source identifier built from an email address or phone number. Epsilon said in 2021 that it would make its identity platform work with UID2, so the two can sit side by side.
- LiveRamp: identity connectivity and a clean room. Compared on its own page.
- Experian and TransUnion: credit bureaus with marketing data and identity units, each covered in a separate comparison.
Sources: AdExchanger on CORE ID and UID2 interoperability; UID2 documentation
Questions to put to Epsilon and every alternative
Ask each vendor the same questions and keep the answers in one document.
- On your own CRM file, what share of records receive an ID, and how many of those reach a device or household?
- Which identifiers and attributes can you export and keep, and which only work inside the vendor platform?
- If you stop buying media, what happens to the data and the audiences built on it?
- How consent was gathered for each source, and how opt-outs reach the copies you hold.
- Who grades the campaign, and can your analysts rerun the numbers on their own?
- The refresh schedule for each field or feed, stated in the contract.
FAQ
- Who owns Epsilon?
- Publicis Groupe. It finalized the purchase of Epsilon from Alliance Data Systems in July 2019.
- What is Epsilon CORE ID?
- Epsilon's identity product. CORE comes from the Conversant One-to-One Relationship Engine, and Epsilon describes CORE ID as a person-level identifier anchored to a verified name and address. It sits underneath the PeopleCloud platform.
- Is GSDSI a replacement for Epsilon?
- Only for part of it. GSDSI licenses data feeds and does not buy media, send email or run loyalty programs. It suits teams that want consumer, identity, CTV, location or property data delivered into systems they control.
- Can we license GSDSI data while working with a Publicis agency?
- Yes. Files arrive by S3, SFTP, Snowflake share or API, and your license sets how they may be used, no matter which agency places your media.
- How do we compare Epsilon with a data licensor fairly?
- Split the evaluation in two. Judge platform and media performance on their own, then test the data on your file, with fill rate, freshness, what you can export and exit terms written down before the test starts.