We recently addressed issues affecting file uploads in Box. We would like to take the opportunity to further explain these issues and the steps we have taken to keep them from happening in the future.

Between 4:47 AM PDT and 5:28 AM PDT on June 24, 2026, some users may have experienced difficulties uploading larger files to Box. During this time, chunked uploads of large files may have failed or timed out, while smaller file uploads continued to work normally. The issue occurred when an internal system that temporarily tracks the progress of large, chunked uploads experienced an unexpected failover and lost the in-progress upload information it was holding. The issue resolved once those connections were reset. In addition, we are hardening how our upload service detects and recovers from this kind of interruption to prevent similar issues in the future.

Analysis

Large file uploads in Box are split into multiple parts and rely on a shared internal caching system to track the progress of each upload while it is in flight. During this incident, that caching system underwent an unexpected failover, and the newly promoted instance did not contain all of the in-progress upload state. As a result, affected sessions could not continue and returned errors. Recovery was further delayed because the upload service continued to use a connection that was no longer valid. Standard file uploads do not depend on this system and were not affected.

Corrective Actions

Box has initiated the following corrective actions:

• Adding dedicated monitoring and alerting for this caching system so that similar failures are detected and corrected more quickly.
• Improving how the upload service detects a lost connection and reconnects automatically, so that recovery is faster and does not require manual intervention.
• Strengthening the resilience of large-upload session storage so that a failure of this caching system has reduced impact on in-progress uploads.

We are continuously working to improve Box and want to make sure we are delivering the best product and user experience we can. We hope we have provided some clarity here and we would be happy to answer any questions you may still have regarding this matter.

Sincerely,

The Box Team