Tipping is a problem in the U.S. It’s often not clear when tipping is appropriate or expected (Uber, anyone?), and this uncertainty can lead to overtipping or undertipping. The whole enterprise is a subtle art that involves reading social signals and understanding unspoken rules, which can lead to great anxiety.

In the mobile era, this led to a storm of tip calculators, as well as apps that facilitate the actual sending of tips. Here are a few of those — there may be dozens more out there. They don’t solve the fundamental problem — Should I tip now or not? — but may ease some of the awkwardness when you decide to drop some (virtual) cash. There are also apps that make payment, including the tip, invisible, such as Velocity and TabbedOut — those are not considered here.

1. Bravo allows servers to set up codes that customers can use to tip or pay. Why “pay”? Because money given to a sidewalk musician may not be considered a tip
2. Global Tipping‘s value proposition is that it helps tip around the globe. It features a comprehensive dashboard to calculate tips and split bills (separating out drinkers and nondrinkers, and people who arrived after the appetizer.)
3. Gratuity is a tip calculator, but is included here because it also allows users to rate the service and attach that rating to the restaurant. It’s not clear where this data goes, but it would be of interest to servers to see the correlation (or lack of one) between perception of service and tip amount.
4. Gratuu, currently in beta, allows users to search staff IDs and send them tips via peer-to-peer payments. It also features a Tip Jar for pooling payments among servers. Gratuu is a product of Just Tipit Ltd, and may have been renamed, because the Tipit app is a virtual reality app.
5. Oppa calls itself a social tip jar, and is “Like Instagram… with money.” It seems to have less to do with rewarding servers for good service, and more with sending money to people you don’t know (“Discover new friends & fans locally & around the world”), whose pictures you happen to admire. Tips max out at $99.
6. Thanks! is “your feel-good payment app” for all those times you don’t have cash — tipping bellhops, valet parking attendants, and the person at the nail salons.
7. TipGenie targets workers behind the scene, such as hotel maids, who often miss out on tips, but won’t anymore, if they leave a QR code provided by TipGenie. The app features significant social options, such as a leaderboard and messaging.
8. Tipping Circle ties into PayPal and social networks, and allows users to set up fundraisers and tip buckets. It also features messaging and social sharing. It’s a lot like Venmo, but with a few added features.
9. Tipsta also features QR codes, so you can tip your “hairdresser, nail technician, valet etc.” The app went live yesterday.