OnlineOrNot alternative: broader checks, no per-monitor add-ons

What OnlineOrNot does well

It is a focused, independently run product, and the browser checking is the part worth paying attention to.

• Browser checks are a first-class product, not an afterthought. Running a real headless browser through a login or a checkout catches the class of failure where the server returns 200 and the page is still broken. Undownable does not do this at all.
• Metered browser check runs mean you pay for what you use rather than buying a tier that includes a large allowance you never touch.
• The free Hobby plan includes browser check runs, which is unusual: most services reserve browser checking entirely for paid plans.
• Thirty second intervals on the paid plan, faster than Undownable offers.
• Unlimited team members on the paid plan, so collaboration is not seat-taxed.
• On-call integrations, maintenance windows, and an audit log on the paid plan.
• It is built in the open by a small independent team, which some buyers value and which usually means responsive support.

Where it starts to hurt

• The free plan carries three uptime monitors. That is a genuinely small number, and most people outgrow it within a week of setting up.
• Monitors beyond the included paid allowance are bought in blocks, so growth arrives as a series of upgrade decisions rather than headroom you already have.
• Each additional status page carries its own monthly charge, which adds up fast if you run a page per product or per client.
• Browser check runs are metered, so a flaky check that retries can quietly consume allowance.
• History retention on the free plan is short, at a fortnight.
• The bill has several moving parts, which is precisely the thing people are trying to escape when they search for an alternative.

Side by side

Where Undownable differs

• Ten monitors on the free plan rather than three, with every alert channel included, so a free account is actually usable rather than a demonstration.
• Fifty monitors on Pro with nothing to add on. No monitor blocks, no metered runs, no per-status-page fee.
• Unlimited status pages on Pro, each on its own custom domain. If you run a page per client, this is the difference between a flat bill and a growing one.
• A broader set of protocol-level check types: HTTP and HTTPS, keyword matching, JSON API assertions with dot notation into the response body, TCP ports, ping, DNS records, SSL certificates, and push heartbeats.
• SSL checks that verify the full chain and the hostname rather than only the expiry date, with escalating warnings at 30, 14, 7, and 1 days out and an all-clear when renewed.
• Push heartbeats for cron jobs, backup scripts, and self-hosted monitoring boxes, in the same account and on the same alert routing.
• A degraded state distinct from down, exactly-once alert delivery, flap suppression, and confirmation thresholds so a single blip never pages anyone.
• First class ntfy support including self-hosted ntfy servers with access tokens.
• A first-party MCP server alongside the versioned REST API, both with least-privilege tokens pinnable to a single team.
• 365 days of history on Pro and 30 days on Free.

Who should stick with OnlineOrNot

• You need browser checks. This is the deciding line: if you must verify that a login flow or a checkout still works end to end, OnlineOrNot does it and Undownable does not.
• You need thirty second intervals.
• You prefer usage-based billing and genuinely want to pay only for the runs you consume.
• You need SMS alerting or an on-call escalation integration.
• You want an audit log of who changed what in the monitoring configuration.
• You are already on the free plan, only need three monitors, and the browser check allowance is what you actually came for.