On May 5, 2026, Klaviyo experienced a critical platform-wide outage that lasted 49 hours and 38 minutes. This was not a partial degradation. Thirteen components went down, including email sending, flow processing, the app itself, signup forms, analytics, segmentation, and mobile push. Klaviyo confirmed that data from API requests that received errors during the incident was lost. For stores that depend on Klaviyo for email revenue, flows, and customer data, this was the worst outage in the platform's recent history.
Timeline of the May 5-7 Klaviyo outage
May 5, 5:24 PM EDT: Klaviyo begins experiencing service disruptions. Users cannot log in. Campaign and flow email sending stops. The Klaviyo app becomes inaccessible.
May 5, evening: The scope of the outage becomes clear. Thirteen separate components are affected: the Klaviyo App, Email Deliverability, Profiles, Signup Forms, Unsubscribe and Preference Pages, Campaign Email Sending, Flow Email Sending, Email Content, Mobile Push Sending, Reviews, List Subscription, Analytics, and Segmentation. APIs return errors.
May 6, throughout the day: The outage continues. Stores with campaigns scheduled for Tuesday morning have no way to send, hold, or reschedule. Flows that should be firing (abandoned cart, post-purchase, browse abandonment) are not processing. Signup forms on storefronts are broken, meaning new subscriber captures are lost.
May 7, 7:02 PM EDT: Klaviyo posts resolution. Services are restored progressively, with background data reconciliation continuing after the main systems come back online. Total duration: 49 hours 38 minutes.
Data loss: the part that matters most
Klaviyo confirmed that "data from API requests that received an error during the incident were lost." This is a critical detail. For Shopify stores, the Klaviyo integration sends events to Klaviyo via API: orders placed, checkouts started, products viewed, customers created. Any of these events that failed during the 49-hour window are gone.
What this means in practice: a customer who placed an order during the outage may not have that order recorded in their Klaviyo profile. A post-purchase flow that should have triggered for that customer will not fire. A segment based on "placed order in the last 7 days" will be missing those customers. The downstream effects of lost event data ripple through your entire email marketing operation for weeks.
The cascading aftermath: May 7-8
The outage did not end cleanly. On May 7 at 9:32 PM EDT, less than 3 hours after the main outage was marked resolved, a new incident began: processing delays caused by an upstream AWS disruption. This lasted another 17 hours and 33 minutes, affecting segmentation, analytics, reporting, and campaign and flow processing.
The next day, May 8, brought another incident: campaign and flow page loading errors lasting 9 hours 29 minutes, again attributed to AWS instability combined with increased retry traffic from the recovery.
In total, from May 5 to May 8, Klaviyo experienced roughly 76 hours of degraded or non-functional service across three overlapping incidents. For stores running email as a primary revenue channel, this was effectively a four-day blackout.
The revenue math
Consider a mid-size Shopify store with a 25,000-subscriber list that sends 2 to 3 campaigns per week and relies on automated flows for abandoned cart recovery, post-purchase sequences, and browse abandonment:
- Two scheduled campaigns during the outage window that could not send. Expected revenue per campaign: $1,000 to $2,000. Lost: $2,000 to $4,000.
- Abandoned cart flows that did not trigger for 49+ hours. A store with $5,000 in abandoned carts per day and a 10% email recovery rate lost roughly $1,000 in recoverable revenue per day, or $2,000+ over the outage window.
- Post-purchase flows (review requests, cross-sells) that did not fire. These have lower immediate revenue impact but compound over time.
- Signup form downtime. New subscriber captures lost during the outage window are gone permanently. A store adding 50 subscribers per day lost 100+ potential subscribers.
Total estimated impact for a mid-size store: $4,000 to $7,000 in direct and attributable revenue, plus the ongoing cost of lost event data affecting segmentation and flow targeting for weeks afterward.
Why Klaviyo outages are uniquely expensive
Stripe failures are loud. Checkout breaks visibly and customers tell you. Klaviyo failures are quiet. During shorter outages, emails enter a send queue that looks normal from the inside but is not delivering. You think you sent 18,000 emails. You sent zero.
The May 5-7 outage was so severe that even the dashboard was inaccessible, which made the failure obvious. But shorter Klaviyo outages are far more dangerous because they are invisible. A campaign that silently fails to deliver during a 2-hour degradation may not be noticed until your daily revenue report shows zero email-attributed sales.
Klaviyo does not automatically resend campaigns that fail during an outage. Once a campaign's send window closes, the missed emails are gone. You can manually resend to the original list later, but a Tuesday morning promo that arrives Thursday afternoon performs a fraction as well. The revenue is largely lost.
What to do when Klaviyo has an outage
- Know immediately. The worst outcome is finding out hours later because your email revenue was zero. StatusBird monitors Klaviyo every 2 minutes and alerts you via SMS, email, or Slack the moment the status changes.
- Do not schedule new campaigns. If you know Klaviyo is degraded, hold any campaigns you were about to send. Send them once delivery is confirmed restored.
- Check your delivery data after recovery. Do not trust the "Sent" count in Klaviyo's dashboard. Check delivery rates and actual opens for sends during the outage window. If delivery rate is near zero, the campaign did not go out.
- Audit for lost event data. After a major outage, compare Shopify order counts against Klaviyo profile events for the outage window. If events are missing, you may need to manually trigger flows or re-sync data.
- Decide on resends. For high-value campaigns that failed to deliver, a same-day resend after resolution is often worth it. Acknowledge the delay with a light-touch subject line rather than resending the identical email.
- Audit your flow backlog. Check whether abandoned cart, browse abandonment, and post-purchase flows fired normally during the outage window. Missing triggers typically cannot be retroactively re-sent, but knowing the gap helps you estimate total impact.
The May 2026 outage was Klaviyo's worst incident in recent history: 49 hours of complete platform failure with confirmed data loss. Monitoring Klaviyo's status is not optional for stores where email is a primary revenue channel.