Uptime percentage explained for indie SaaS (without a legal SLA)
Sales decks throw 99.9% around. Customers ask what it means. Lawyers ask what you guaranteed. If you did not sell an SLA, your status page should show measured uptime honestly — not contract language you cannot back.
StillOnline displays probe history on stillonline.tech/s/{id} — 24 hours on Free, 90 days on Pro/Ultimate (pricing). This guide translates percentages for comms and internal goals.
Quick answer
99.9% monthly uptime allows roughly 43 minutes of downtime per month (30-day month). 99.95% ≈ 22 minutes. StillOnline calculates uptime from external HTTP probes on your registered URL — not application traces. Show the hosted history link in sales docs; do not copy enterprise SLA credits unless your terms actually offer them. Free tier retention is 24 hours; quote longer windows only on paid plans.
The math (simple)
| Target | Downtime budget (30-day month) |
|---|---|
| 99% | ~7.2 hours |
| 99.9% | ~43 minutes |
| 99.95% | ~22 minutes |
| 99.99% | ~4.3 minutes |
Source: standard high availability arithmetic — downtime minutes ≈ (1 - availability) × 43,200 minutes/month.
Probes run every 5 minutes on Free — a 10-minute red episode (two fails + recovery) is one visible blip, not necessarily a full 10 minutes of customer impact if you recover fast.
What StillOnline measures
| Included | Not included |
|---|---|
| HTTP status on your health URL | Per-user session success |
| SSL check failures (if configured) | Third-party Stripe unless you monitor it |
| PROBE_LIMITED yellow (antibot) — not counted as DOWN | Internal queue depth unless in /health |
See false positive tuning and health design.
How to talk to customers without an SLA
Do:
- Link the status page with visible history — B2B trust.
- Say “we publish external monitoring results.”
- Use incident summaries after outages — incident template.
Do not:
- Promise 99.9% in contracts without engineering + legal review — Google SRE on SLOs warns against targets you do not measure and staff.
- Compare to competitors’ SLA credits in blog posts without facts.
Related guides
- Public status page guide
- B2B procurement small deal
- Incident update cadence
- False positive uptime tuning
FAQ
Does StillOnline guarantee 99.9% for my product?
No. StillOnline measures and displays your URL probes; your legal uptime promise is separate.
Does maintenance count against uptime?
If you take the health URL down during maintenance, probes go red — schedule maintenance and communicate.
One blip — how much does it hurt 99.9%?
~10 minutes down uses roughly a quarter of a 43-minute monthly budget at 99.9%.