Smart contract monitoring: what to watch and which tool to pick
Smart contract monitoring means watching what happens on your contract, through the events it emits and the token balances it holds. When something leaves its normal range, you get an alert. Tools differ in four ways:
- whether they are hosted or self-hosted;
- which chains they cover;
- how they set the limit: fixed thresholds or a learned baseline;
- whether they only alert or also act.
What to monitor
Ownership and roles
OwnershipTransferred,RoleGranted, upgrades.Value moving
Large transfers, a balance dropping below a floor, a burst of withdrawals.
Health
A drop in normal activity, an event that stopped firing, a spike in liquidations.
Admin actions
Pause, unpause, parameter changes.
Tools compared
| Tool | Type | Chains | How limits are set | Channels | Price to start | Best for |
|---|---|---|---|---|---|---|
| SmartAlertus | Hosted | Ethereum, BNB Chain, Base, Arbitrum | Fixed threshold, or a baseline for every hour of the day; rules checked on history | Telegram, Slack, Discord, PagerDuty, email, webhook | Free; Pro $30/mo | Small teams that want working alerts in minutes |
| OpenZeppelin Monitor | Self-hosted, open source | EVM, Stellar, Solana | Fixed conditions | Slack, Discord, Telegram, email, webhook | Free (AGPL); your servers | Teams with DevOps that want full control |
| Tenderly Alerts | Hosted platform | 97+ networks (platform-wide) | Fixed triggers, 12 types | Email, Slack, Telegram, Discord, PagerDuty, webhook | Paid plan, contact sales | Teams already using Tenderly for debugging and simulation |
| Forta | Risk platform, chain firewall, detection-bot network | Firewall on Ink, Celo, Plume and others | Defined in bot code | Email, webhook, API | Demo, no public price | Chains and larger protocols that need screening before execution |
| Hypernative | Enterprise security platform | 70+ | ML-based threat detection | Slack, Telegram, PagerDuty, OpsGenie, webhook | Demo, no public price | Large protocols with a security budget |
| Alchemy Webhooks | Event delivery to your server | Many, one network per custom webhook | Address and GraphQL filters; alert logic is your code | HTTP webhook only | Free: 30M CU/mo; then $0.525 per 1M CU | Teams that want raw events and will build the alerts |
| KeeperHub | Hosted automation | 20 EVM + Solana | Event filters | Slack, Discord, email, Telegram, webhook | Free tier; Pro $49/mo | Monitoring plus automated transactions |
- Type
- Hosted
- Chains
- Ethereum, BNB Chain, Base, Arbitrum
- How limits are set
- Fixed threshold, or a baseline for every hour of the day; rules checked on history
- Channels
- Telegram, Slack, Discord, PagerDuty, email, webhook
- Price to start
- Free; Pro $30/mo
- Best for
- Small teams that want working alerts in minutes
- Type
- Self-hosted, open source
- Chains
- EVM, Stellar, Solana
- How limits are set
- Fixed conditions
- Channels
- Slack, Discord, Telegram, email, webhook
- Price to start
- Free (AGPL); your servers
- Best for
- Teams with DevOps that want full control
- Type
- Hosted platform
- Chains
- 97+ networks (platform-wide)
- How limits are set
- Fixed triggers, 12 types
- Channels
- Email, Slack, Telegram, Discord, PagerDuty, webhook
- Price to start
- Paid plan, contact sales
- Best for
- Teams already using Tenderly for debugging and simulation
- Type
- Risk platform, chain firewall, detection-bot network
- Chains
- Firewall on Ink, Celo, Plume and others
- How limits are set
- Defined in bot code
- Channels
- Email, webhook, API
- Price to start
- Demo, no public price
- Best for
- Chains and larger protocols that need screening before execution
- Type
- Enterprise security platform
- Chains
- 70+
- How limits are set
- ML-based threat detection
- Channels
- Slack, Telegram, PagerDuty, OpsGenie, webhook
- Price to start
- Demo, no public price
- Best for
- Large protocols with a security budget
- Type
- Event delivery to your server
- Chains
- Many, one network per custom webhook
- How limits are set
- Address and GraphQL filters; alert logic is your code
- Channels
- HTTP webhook only
- Price to start
- Free: 30M CU/mo; then $0.525 per 1M CU
- Best for
- Teams that want raw events and will build the alerts
- Type
- Hosted automation
- Chains
- 20 EVM + Solana
- How limits are set
- Event filters
- Channels
- Slack, Discord, email, Telegram, webhook
- Price to start
- Free tier; Pro $49/mo
- Best for
- Monitoring plus automated transactions
OpenZeppelin Defender used to be the default hosted option. It has been retired: no new sign-ups since June 2025, shut down on July 1, 2026. See Defender alternative.
Side by side: SmartAlert vs Tenderly · vs OpenZeppelin Monitor · vs Forta · vs Hypernative · vs Alchemy Webhooks
How to choose
- 1
Only need alerts, and no one to run servers?
Pick a hosted tool: SmartAlert, Tenderly or KeeperHub.
- 2
Activity changes through the day?
Fixed thresholds will be noisy or late. Look for a per-hour baseline (SmartAlert).
- 3
Need to block exploits, not just see them?
Use a security platform: Hypernative or Forta.
- 4
Need many chains?
OpenZeppelin Monitor, Tenderly or Hypernative. SmartAlert covers Ethereum, BNB Chain, Base and Arbitrum.
- 5
Need alerts on function calls?
Tenderly or OpenZeppelin Monitor. SmartAlert watches contract events, failed transactions, view functions and token balances.
- 6
Need an on-chain reaction after the alert?
KeeperHub or OpenZeppelin Relayer.
FAQ
What is the difference between monitoring and security tools?
Monitoring tells you what changed on your contract. Security platforms try to detect and stop attacks. Many teams use both.
Why a baseline instead of a threshold?
Activity at 3 a.m. and at 3 p.m. is different. A baseline compares each hour with the same hour on previous days, so one rule works day and night.
Can I try SmartAlert for free?
Yes. Free includes Telegram alerts. A new project gets Pro limits for 14 days, no card needed.
Sources (checked Oct 20, 2026)
- https://docs.openzeppelin.com/monitor
- https://docs.tenderly.co/alerts/intro-to-alerts
- https://tenderly.co/pricing
- https://docs.tenderly.co/supported-networks
- https://docs.forta.network/en/latest/getting-started/
- https://www.hypernative.io
- https://keeperhub.com/pricing
- https://docs.keeperhub.com/guides/defender-migration
- https://www.openzeppelin.com/news/defender-sunset-faq
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.