Some of the images online are truly eye-popping. They range from landscapes and portraits to accident photos and images from historical events. The built-in search function helps you locate photos that suit your interests.

Be aware that anyone who can see your photos can also download them, though they’ll typically only get a lower-resolution copy of the original that wouldn’t be suitable for printing but could easily be e-mailed around or posted elsewhere on the Web.

In some cases, you can even comment on photos — adding an “attaboy’’ for ones you like, or offering further information about a scene or event that you recognize.

Flickr is still in test mode, and sometimes its servers are burdened by the crush of visitors and photos it is handling. But for free online photo-sharing, it’s hard to beat the site’s combination of features and flexibility.