Mem0 vs Zep: Which Agent Memory Layer Should You Pick in 2026?

If you are choosing a memory layer for an LLM application in 2026, Mem0 and Zep are probably both on your list. They are often described as competitors, and they are, but they are built around different ideas of what memory is. Understanding that difference is most of the decision.

The Short Version

Memory Model

Mem0 treats memory as a set of short statements. You pass a conversation to add, an LLM extracts the facts worth keeping ("prefers vegetarian food," "working on a Postgres migration"), and Mem0 decides whether each one is new, an update to an existing memory, or a duplicate. Memories are scoped by user_id, agent_id, or run_id. A graph memory option stores entities and relationships alongside, but the primary unit stays the extracted fact.

Zep treats memory as a graph. Conversations and documents are ingested as episodes; Graphiti extracts entities and relationships and writes them as nodes and edges, each edge carrying the time it became valid and, when superseded, the time it stopped being valid. The result is a knowledge graph per user, with group graphs for data shared across users. Zep assembles a context block from the graph for each prompt.

The practical consequence: Mem0 is better at "what does this user like," Zep is better at "how are these things related and what changed."

Retrieval

Mem0's search embeds the query and returns the most similar memories for the given scope, with metadata filters and optional reranking. It is fast and predictable, and for personalization it is usually sufficient.

Zep's retrieval is hybrid: semantic and keyword search over nodes, edges, and episodes, with graph expansion to pull in connected facts, and reranking before assembling the context block. On multi-hop questions and questions involving change over time, this is the stronger approach. For a deeper look at why, see knowledge graphs and LLMs and temporal knowledge graphs.

Handling Change

This is where the two diverge most. When Mem0 sees a fact that conflicts with a stored memory, it updates or deletes the old one. History is not kept, and you cannot ask what was true last month.

Zep closes the old edge's validity interval and opens a new one. The graph answers "what is current" by default and "what was true on a date" on request. For assistants that run for months, this is a real advantage: stale facts stop leaking into answers, and corrections are auditable.

Hosting and Ownership

Mem0's core library is open source under Apache 2.0 and runs on your infrastructure with your choice of vector store and LLM. The managed platform adds hosting, a dashboard, and some features not in the library.

Zep's Graphiti framework is open source under Apache 2.0 and can be run on your own graph database. The Zep platform — the hosted product with the per-user graph, context assembly, and dashboard — is proprietary and managed-only. Teams with strict data residency or air-gap requirements either build on Graphiti directly or look elsewhere.

Pricing Shape

Both offer free tiers for development and usage-based paid plans; exact numbers change, so check the current pages. The shape matters more than the figures: Mem0 bills around memory operations and storage, Zep around processed data and retrieval. In both cases cost scales with how much you ingest and how often you retrieve, so estimate from your real traffic rather than list prices.

Which One to Choose

• Choose Mem0 if you are personalizing a chat product for individual users, want the simplest possible API, and do not need relationships or history.
• Choose Zep if your assistant runs long enough that facts change, you want temporal reasoning out of the box, and a managed-only platform is acceptable.
• Choose neither if you need many agents sharing one memory, domain structure through an ontology, hybrid retrieval that learns from feedback, and the whole system self-hosted — on a single Postgres if you want.

Where cognee Fits

cognee is an open-source (Apache 2.0) memory engine that combines what each of the two does well and adds what neither does. Like Zep, it builds a knowledge graph with temporal extraction and contradiction resolution. Like Mem0, the whole thing is open source and self-hostable. Unlike both, it is designed as shared memory for many agents: typed entities with optional ontologies, hybrid retrieval that walks the graph and ranks by learned importance, a self-improving improve step, and an MCP server so coding agents and assistants share the same memory. Hosting ranges from Neo4j or Kuzu to everything on one Postgres, and memory is exportable in the open COGX format.

The dedicated comparisons go deeper: cognee vs Mem0 and cognee vs Zep. If you are already on one of them, there are migration guides for Mem0 and Zep, and a broader Mem0 alternatives roundup.

Is Zep better than Mem0?+

For relationships and change over time, yes: Zep's temporal knowledge graph keeps history and avoids stale facts. For simple per-user personalization with the least setup, Mem0 is the easier choice.

Can I self-host Zep?+

You can self-host Graphiti, Zep's open-source graph framework. The Zep platform itself, with the per-user graph and context assembly, is a managed service.

Does Mem0 have a knowledge graph?+

Mem0 offers a graph memory option that stores entities and relationships alongside its extracted memories. The primary memory unit remains the flat fact, and temporal validity is not modeled.

What is an alternative to both Mem0 and Zep?+

cognee combines a temporal, typed knowledge graph with full open-source self-hosting and shared memory for many agents. Other options include Letta, Hindsight, and LangMem, compared in the Mem0 alternatives guide.