Short answer: there aren’t many reputable uptime monitors that include truly unlimited free SMS alerts. The best practical approach is to use a free uptime monitor that can send email/webhooks, then convert that to SMS via either a carrier “email-to-SMS” gateway or a small SMS gateway (Twilio/Plivo) or an automation service (IFTTT/Zapier). That gives you reliable free (or very low-cost) SMS alerts.
Below are simple, practical options and setup steps.
Recommended free monitors to use
- UptimeRobot (free tier): 50 monitors, 5‑minute checks, alerts via email, push, Slack, webhooks. No free native SMS, but you can route email/webhook → SMS.
- Freshping (Freshworks) / StatusCake / Cronitor / Healthchecks.io: free tiers with email/webhook notifications. Check feature list for each; same routing approach applies.
Two ways to get SMS alerts for free/cheap
A) Email‑to‑SMS carrier gateway (usually free)
- Many mobile carriers provide an email-to-SMS gateway: you send an email to number@carrier-sms-gateway and it’s delivered as an SMS.
- Common US examples:
- AT&T: number@txt.att.net
- T‑Mobile: number@tmomail.net
- Verizon: number@vtext.com
- Sprint (now T‑Mobile): number@messaging.sprintpcs.com (may vary)
- Steps:
- In your uptime monitor, add an alert contact that uses email. Use the SMS gateway address for the destination (e.g., 12125551212@vtext.com).
- Test a down/up event and confirm you receive the SMS.
- Pros: free, simple.
- Cons: relies on carrier gateways (can be slow, truncated messages, not internationally consistent). Requires knowing the recipient carrier. Some carriers block long or automated messages.
B) Use a small SMS gateway (Twilio / Plivo / Vonage) with webhook
- Twilio trial gives free credits and lets you send SMS via API/webhook from most monitors that can call a webhook.
- Steps (example Twilio):
- Sign up for Twilio (trial credits).
- Create a small webhook endpoint (or use Zapier/IFTTT) that accepts monitor webhooks and uses Twilio API to send an SMS. Some monitors let you configure a direct webhook URL.
- Configure your monitor to call that webhook on down/up events.
- Pros: reliable, international, controllable text content, can send to any number.
- Cons: not free long-term (but inexpensive); requires a small setup.
Automation services (IFTTT, Zapier, Make)
- If your monitor supports webhooks, you can use an automation service to translate the webhook into an SMS action.
- IFTTT supports SMS in some regions; Zapier can call Twilio to send SMS.
- Useful if you don’t want to write code.
Practical tips and caveats
- Monitoring interval: free tiers often limit to 1‑5 minute checks. Don’t expect instant detection like enterprise services.
- Rate/lifetime: carrier email‑to‑SMS gateways may truncate messages and sometimes block automated messages. Use short messages with key info (site name, status, time, URL).
- Reliability: for business‑critical services, paid SMS or phone call alerts are recommended.
- Security: if using an open webhook, add a secret/token to avoid spoofed alerts.
- International numbers: email gateways vary widely; Twilio or paid services are better for non‑US recipients.
- Test thoroughly: simulate downtime to confirm alert chain.
Example minimal setups
- Minimal free: UptimeRobot (email alerts) → recipient’s carrier email gateway (number@vtext.com). No code.
- Reliable low-cost: UptimeRobot (webhook) → small Twilio webhook (or Zapier) → SMS. One‑time small setup, pay per SMS.
If you tell me:
- which country/carrier and how many phone numbers you need to alert,
- whether you prefer zero-code or you’re comfortable with a small script,
I can give a step‑by‑step configuration for the best option.