Yahoo photo-sharing site Flickr is alerting users that the site plans to be out of commission for about six hours Wednesday, as it undertakes some "planned maintenance."
The site will be unavailable from 4 p.m. PT / 7 p.m. ET Thursday until 10 p.m. PT Thursday and 1 a.m. ET Friday.
"During this time, Flickr will be unavailable on web and mobile, and the API will not be reachable," Flickr says on its blog. "There will also be a site-wide notice an hour beforehand to make sure no one is taken by surprise."
The six-hour outage is an unusually long one for such a heavily trafficked site. According to Yahoo, Flickr has 80 million visitors worldwide, with 20 million of those being in the U.S. There are 4.5 million photos uploaded to Flickr daily,
NBC News asked Yahoo for an explanation regarding the lengthy downtime. A Yahoo spokesperson did not go into details, but said via email that, "From time to time, we need to do site maintenance to ensure that we're providing a robust and scalable experience for our users. We appreciate our users' understanding and apologize for any inconvenience."
There have been other recent Flickr outages that weren't planned. The most notable was in May, four days after Flickr released a major update that included a redesign of the site, 1 terabyte of image storage for each user, and support for up to a full 3 minutes per video at 1080p HD quality.
Between then and up until last week, there were also some problems, including these:
Flickr, like other photo sites, faces increasing competition from Facebook, Instagram (owned by Facebook) and Twitter's Vine.
In the meantime, if you're on the verge of posting big batches of those summer wedding or vacation photos or video files, check on Flickr's status late Thursday and early Friday morning via its Twitter page.
This story was updated at 6:55 p.m. ETWednesday.