After three years of development, the site, started by The Pirate Bay co-founder Peter Sunde and equivalent to an Internet tip jar, announced its open beta release on Thursday.
Sunde described the site as "not actually micropayments, it's nanopayments" in an FT.com Tech Blog article last month.
Unlike PayPal, Flattr, which is based in Limhamn in southwestern Malmö, charges a minimal €2 (18.90 kronor, $2.60) monthly fee from which a user can send funds to the websites he or she wishes to support.
The site, named both for flattering someone and a flat-rate payment model, believes it is attractive to users who would otherwise hesitate to donate amounts under €10 since users can donate as little as €0.01 - or less.
Users who wish to solicit funds can add a Flattr button to their website. When visitors click on the buttons, the amount the user chooses to donate is transferred.
Prior to the open beta launch, the site had 20,000 members by invitation tipping an average of €0.15.
Initially, Flattr will charge a 10 percent of each user's monthly fee, a figure which will drop as the service attracts more users.
Despite comparing its service to PayPal's, the only two ways to deposit money into a user's account is by Visa, MasterCard or Nordea through Moneybookers or PayPal, both of which deduct fees from the original sum.
Already, the site has produced tangible figures, especially in Germany. Newspaper site Taz.de received €988.50 in June from Flattr, while Netzpolitik.org earned €576.53 or €0.25 per click in the same period, FT.com reported
Separately, a photographer has received €33 from 90 clicks from two Flattr buttons and a group of American sewing bloggers also counts itself among Flattr's early adopters.
According to the FT.com report, among the site's investors are Last.fm's first investor and chairman, Stefan Glaenzer and Eileen Burbidge, formerly at Skype, who added she is unconcerned about Sunde's Swedish court conviction in The Pirate Bay case.