App development falls in Class 42, tech & software services, and depending on what exactly you sell it can also fall in Class 9 or Class 40 or Class 38. Everything below is read from the USPTO's own list of accepted descriptions, not from an opinion about where it belongs.
Searching the USPTO Trademark ID Manual for app development returns 26 accepted descriptions, and most of them sit in Class 42. The manual is the list of identifications the office has already approved, so wording taken from it is pre-approved and settles the class at the same time.
The class follows from the identification you write, so "what class am I in" is really "what exactly do you sell". How the class system works covers the rest.
Software as a service (SaaS), app development, IT, design, or science and engineering services.
18 accepted descriptions in the manual mention app development. For example:
Software, apps, downloadable content, computers, or electronic devices.
4 accepted descriptions in the manual mention app development. For example:
You treat, process, or custom-make materials and goods for others.
2 accepted descriptions in the manual mention app development. For example:
Telecommunications like phone, internet access, or messaging services.
1 accepted description in the manual mention app development. For example:
App development appears in 4 classes because what you make, what it is made of and the service of selling it are separate classes. Pick the descriptions above that match what you actually do.
App development is a service, so it sits in Classes 35 to 45. Software that delivers a service is often Class 9 or Class 42 as well.
Technology and design services: software as a service and architectural design are here. Software the customer downloads is a good instead, so downloadable software is Class 9.
The class decides what a registration covers; it does not decide whether the name is available. Relatedness is judged on the identifications, so a conflict can sit in a class you never looked at: the same name in a different industry.
Check whether your name is clear for app development Searches the live USPTO register, including sound-alike and meaning-alike names. First search $2, then $5.App development sits in Class 42, tech & software services. That is where the USPTO's own ID Manual puts it: 18 accepted descriptions mentioning app development fall in Class 42. Depending on exactly what you sell it can also fall in Class 9 or Class 40 or Class 38.
You file in every class you actually use the mark in, and the USPTO charges its fee per class. Selling a product and also running an online store for it is two classes, not one. Filing in classes you do not use is worse than filing in too few: an application has to be supported by real use or a genuine intent to use.
No. The class decides what a registration covers. Availability turns on whether someone already holds a similar mark for related goods, and relatedness is judged on what the identifications say rather than on the class number, so marks in different classes can still conflict.
Not what you sell? Search the class finder for your own wording, or browse all 45 classes.