Illustration: Marc Rosenthal In the beginning there was Adobe Photoshop, an awesomely potent--but famously pricey and complex--digital darkroom. Simpler photo editors, such as Adobe's Photoshop Elements and Corel's Paint Shop Pro, now run around $80--not bad, but still an investment. And none of the programs has evolved much to serve millions of shutterbugs seeking simple, easily accessible tools for images shared online via Facebook, Flickr, Picasa, and the like.

Enter a new breed of photo editors that not only leverage the Web but live on it--browser-based services you can use on any PC with an Internet connection. These Web tools let you directly edit images on photo-sharing sites and social networks, so it's easy to tweak images you've posted to the Web without downloading them again; the editors also work with photos stored on your PC's hard drive. As with most Web services, the typical price for browser-based editors is unbeatable: $0.00.

There are several catches, though. No online image editor delivers the wealth of features and precision editing tools that Photoshop Elements and Paint Shop have had for years; most don't even let you print your pictures. Some of these Web-based editors are sluggish, clunky to use, or both. And unlike traditional desktop software, the services work only when the Web itself works--a point that was driven home in July, when Amazon's widely used S3 storage platform suffered an outage that knocked out several online editors.

At their best, though, Web image editors deliver surprisingly strong tools, with decent performance and usability. For this review, I explored half a dozen services: FlauntR, FotoFlexer, Photoshop Express, Picnik, Picture2Life, and Splashup. They all offer basic editing features, including cropping, resizing, and color-adjustment capabilities, plus at least a few fancier effects (for example, the ability to apply Warholesque pop-art colors or warp subjects into cartoony caricatures).

All allow you to work directly with images posted on at least three major photo-sharing sites (see the features chart). None charges fees of any sort except Picnik, which reserves a few features for a Premium edition that costs $25 a year. (FotoFlexer, Picture2Life, and the free version of Picnik carry ads; FlauntR, Photoshop Express, and Splashup don't.)

FotoFlexer and Picnik were clear standouts--and Picnik's uncommonly well-done interface gave it the edge. When you need to quickly tweak a picture on a photo site (or on a PC with no desktop image editing application), it's productive and fun to go Picniking.

Some of the capabilities and limitations of each service are illustrated in our slide show.