Measured over the 180 days ending July 2026, Omnisend has been the more reliable platform: it held a 100% uptime grade (A+) with only 4 minutes of major-incident downtime, while Klaviyo posted 99.81% (B+) with 326 minutes of downtime across 2 major incidents. Both are dependable platforms, but the difference in how long their incidents last is real, and it matters most during a send window.
The numbers, side by side
| Metric (180 days ending July 2026) | Klaviyo | Omnisend |
|---|---|---|
| Uptime (major/critical incidents) | 99.81% | 100% |
| StatusBird reliability grade | B+ | A+ |
| Major or critical incidents | 2 | 2 |
| Total downtime | 326 minutes | 4 minutes |
How these numbers are measured: StatusBird checks each service's status every 2 minutes, around the clock. The uptime figures below count major and critical incidents over the 180 days ending July 2026; brief degraded periods are tracked but excluded from the uptime math so that chronically noisy status pages do not distort the comparison. Full details on the methodology page.
How reliable is Klaviyo?
Klaviyo's 2 major incidents in the window produced 326 minutes of downtime, driven largely by the May 2026 outage, which took campaign sends and flows offline during business hours (full timeline in the Klaviyo May 2026 postmortem). The longer-run picture, including what typically breaks first, is in is Klaviyo reliable and on the live Klaviyo reliability page.
How reliable is Omnisend?
Omnisend also logged 2 incidents, but they totaled just 4 minutes: its incidents in this window were detected and resolved almost immediately. Current status and history are on the Omnisend reliability page, with more context in is Omnisend reliable.
Should reliability decide between Klaviyo and Omnisend?
Not by itself. Feature depth, pricing, and deliverability matter more for most stores, and a B+ is a good grade in absolute terms. The practical takeaway is different: whichever platform you choose, an email platform outage during a planned send (especially around BFCM) silently costs revenue, so you want to know within minutes, not when open rates crater. That is what independent monitoring is for.
Start monitoring your stack free with StatusBird: 1 service, no credit card required. Pro is $29/month for all 84 services with SMS, email, Slack, Teams, and Discord alerts within 2 minutes of a status change.