OpenZeppelin Defender alternative for monitoring
OpenZeppelin has retired hosted Defender: new sign-ups closed on June 30, 2025, and the service shut down on July 1, 2026. If you used Defender Monitor to get alerts from your contracts, SmartAlert is a hosted replacement for that part. You don't need servers or config files. Paste an address, and alerts arrive in Telegram, Slack, Discord or a webhook.
SmartAlert replaces Monitor only. It does not replace Relayer, Actions or Deploy, and it does not sign or send transactions.
SmartAlert vs Defender Monitor vs OpenZeppelin Monitor
| SmartAlertus | Defender Monitor | OpenZeppelin Monitor (open source) | |
|---|---|---|---|
| Status | Available | Retired: no new sign-ups since June 2025, shut down on July 1, 2026 | Available, v1.x |
| Hosting | Hosted (SaaS) | Hosted | Self-hosted only (Rust, Docker) |
| Networks | Ethereum, BNB Chain, Base, Arbitrum | — | EVM chains, Stellar, Solana |
| Setup | Paste a contract address | UI | JSON config files |
| Limit per rule | Fixed threshold, or a baseline for every hour of the day | Fixed conditions | Fixed conditions (filters) |
| Check a rule on history before turning it on | Yes, over the last days of real data | — | Run on a single block |
| Channels | Telegram, Slack, Discord, PagerDuty, email, webhook | — | Slack, Discord, Telegram, email, webhook, scripts |
| Price | Free; Pro $30/mo; Business $99/mo | — | Free (AGPL-3.0); you pay for servers and upkeep |
- SmartAlertus
- Available
- Defender Monitor
- Retired: no new sign-ups since June 2025, shut down on July 1, 2026
- OpenZeppelin Monitor (open source)
- Available, v1.x
- SmartAlertus
- Hosted (SaaS)
- Defender Monitor
- Hosted
- OpenZeppelin Monitor (open source)
- Self-hosted only (Rust, Docker)
- SmartAlertus
- Ethereum, BNB Chain, Base, Arbitrum
- Defender Monitor
- —
- OpenZeppelin Monitor (open source)
- EVM chains, Stellar, Solana
- SmartAlertus
- Paste a contract address
- Defender Monitor
- UI
- OpenZeppelin Monitor (open source)
- JSON config files
- SmartAlertus
- Fixed threshold, or a baseline for every hour of the day
- Defender Monitor
- Fixed conditions
- OpenZeppelin Monitor (open source)
- Fixed conditions (filters)
- SmartAlertus
- Yes, over the last days of real data
- Defender Monitor
- —
- OpenZeppelin Monitor (open source)
- Run on a single block
- SmartAlertus
- Telegram, Slack, Discord, PagerDuty, email, webhook
- Defender Monitor
- —
- OpenZeppelin Monitor (open source)
- Slack, Discord, Telegram, email, webhook, scripts
- SmartAlertus
- Free; Pro $30/mo; Business $99/mo
- Defender Monitor
- —
- OpenZeppelin Monitor (open source)
- Free (AGPL-3.0); you pay for servers and upkeep
“—” means the sources don’t say.
When to choose something else
You have DevOps and want full control
Take OpenZeppelin Monitor. It is free, open source and covers more chains. You will run and update it yourself.
You need chains other than Ethereum, BNB Chain, Base and Arbitrum
SmartAlert covers four EVM networks today. OpenZeppelin Monitor, Tenderly and KeeperHub cover more.
You need automated transactions after an alert (pause a contract, rotate a key)
Look at OpenZeppelin Relayer or KeeperHub. SmartAlert only alerts.
You need exploit prevention
Use a security platform such as Hypernative or Forta. SmartAlert watches activity and health, not attack signatures.
When SmartAlert fits
- You want Defender Monitor-style alerts without running infrastructure.
- Your contract's activity changes through the day, so a single fixed threshold is either noisy in the morning or silent at night. SmartAlert compares each hour with the same hour on previous days.
- You want to see how often a rule would have fired before you turn it on.
Move your monitors in three steps
- 1
Add the contract
Paste the address and pick the network. SmartAlert collects its history; rules start once that finishes.
- 2
Recreate each monitor as a rule
Pick the event or metric, then set a fixed threshold or the baseline. Check the history chart: it shows where the rule would have fired.
- 3
Connect a channel and run in parallel
Add Telegram, Slack, Discord or a webhook, and keep the old setup until the alerts match.
FAQ
Is Defender Monitor still available?
No. OpenZeppelin closed new sign-ups on June 30, 2025 and shut the service down on July 1, 2026. Its recommendation is to self-host the open-source Monitor and Relayer.
Can I import my Defender monitors?
Not automatically. Recreate each monitor as a rule. That usually takes a few minutes per monitor.
Does SmartAlert hold keys or send transactions?
No. It reads public chain data and sends notifications.
Try it on your own contract
An address is enough. The first 14 days get Pro limits, and rules are checked on history before they go live.