On July 1, 2026, OpenZeppelin retires the hosted Defender platform. Your monitors don't vanish: OpenZeppelin ships free, open-source Relayer and Monitor you can run yourself. That's a real, supported path — a good one if you have the ops capacity.
The catch is the word yourself. Self-hosting means standing up Docker images, wiring KMS for signing keys, running the new stack alongside Defender until you've validated it, then cutting over. For teams that chose Defender because it was hosted, that's a project, not a migration.
Sentinel is for those teams. Give us a contract address; we watch it and alert you. Hosted monitoring that stays hosted.
Three steps, no infrastructure.
Paste an address. We watch standard events: large transfers, ownership changes, pause/unpause.
HMAC-signed webhook or email. More coming.
Every flagged event hits your endpoint or inbox, with a full log in your dashboard.
Sentinel watches for specific events and alerts you when thresholds are breached. Nothing it can't detect is listed below.
Large token transfers above your configured threshold
Admin or owner key changes on your contracts
Contract pause triggered by any account
Contract resumed after a pause
What it doesn't (yet): Deep analysis like reentrancy or oracle-failure detection. If event-level monitoring covers your needs, you're in the right place.
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What Sentinel watches today: Transfer, OwnershipTransferred, Paused, Unpaused, with per-contract thresholds. Straightforward, reliable, hosted.
What it doesn't (yet): Deep analysis like reentrancy or oracle-failure detection. If event-level monitoring covers your needs, you're in the right place.
Yes. They offer open-source Relayer and Monitor you can self-host. Here's their official migration guide: https://docs.openzeppelin.com/defender/migration
Sentinel is for teams who want monitoring without running that infrastructure.
Standard on-chain events — large transfers, ownership transfers, pause/unpause — with alert thresholds, via webhook or email.
No. It's event monitoring, not exploit detection. We're clear about that.
Ethereum, Arbitrum, Base, and Polygon. Support for additional EVM chains is on the roadmap.
OpenZeppelin Defender retires July 1, 2026. They offer a free, open-source self-hosted alternative. Read the official migration guide →