Quick Answer
One gap worth knowing: users on OpenZeppelin's forum report there's no open-source replacement for Defender Deploy, which matters if you relied on it for deterministic CREATE2 deployments through hardhat-upgrades.
We make Contract Watch, so read this table knowing that. We've tried to be straight about where the self-hosted tool is the better choice.
Who runs it
OZ Monitor: You do: a binary or Docker container on your own servers
Contract Watch: We do. Nothing to install
Setup
OZ Monitor: JSON files for networks, monitors and triggers, plus your own RPC URLs and notification credentials
Contract Watch: Paste an address and pick a chain
Custom rules
OZ Monitor: Yes. Match events, function calls and transactions with your own filter expressions
Contract Watch: No. A fixed set of security checks
Alert channels
OZ Monitor: Slack, Discord, email, Telegram, webhooks, custom scripts
Contract Watch: Email and the dashboard
Proxy upgrade alerts
OZ Monitor: Build a monitor for the Upgraded event
Contract Watch: Built in. Reads the implementation slot, so upgrades without an event are caught too
Safe signer, threshold and module changes
OZ Monitor: Configure one monitor per event
Contract Watch: Built in, including guard changes and a swapped core contract
EIP-7702 wallet delegations
OZ Monitor: Not a preset; you'd write the rule
Contract Watch: Built in for watched wallets
Scan of the new code after an upgrade
OZ Monitor: No
Contract Watch: Yes, with an AI review on Pro
Automated responses
OZ Monitor: Custom scripts can run when a rule matches
Contract Watch: None. Alerts only
Chains
OZ Monitor: EVM networks and Stellar
Contract Watch: Ethereum, BNB Chain, Polygon, Arbitrum, Optimism
Check speed
OZ Monitor: As fast as you configure it to poll
Contract Watch: Every 5 minutes
Cost
OZ Monitor: Free software; you pay for servers and RPC
Contract Watch: Free for 1 address, up to 10 on Pro
You have an engineer who can own a service, and you need custom rules or Slack alerts
Self-host OpenZeppelin Monitor. It's the closest thing to what Defender Monitor did, and it's free software. Budget a day to migrate and some ongoing time to keep it running.
You're a small team and you mostly want to know when upgrades, ownership or Safe signers change
Contract Watch covers that in a couple of minutes with nothing to host. Add the custom-rule tool later if you outgrow it.
You hold enough value that minutes matter
Monitoring alone isn't enough at that size. Put timelocks on upgrades, rate limits on hot wallets and a sensible Safe threshold in place, and look at a dedicated real-time security platform. Run one of the options above as a second, independent alarm.
On October 29, 2026 an attacker turned Binance's "Binance 14" hot wallet into a contract with an EIP-7702 delegation at 20:20:59 UTC and drained it at 20:24:23. That's 3 minutes and 24 seconds. A monitor polling every 5 minutes could have fired just before the money moved or just after. A monitor that only watched for the Upgraded event would never have fired at all, because nothing was upgraded: the wallet's code was swapped. The delegation then stayed in place for 3 hours 49 minutes until Binance revoked it at 00:10:35. Pick a tool that watches the right things, and put the limits in place that stop a drain from finishing in one transaction.
The full Binance 14 timeline