Consider something like, "2013-2015: built a tool that does (whatever) for a failed startup". Include details about what you built and in what language and so

Consider something like, "2013-2015: built a tool that does (whatever) for a failed startup". Include details about what you built and in what language and so forth on the resume, but leave out the company name (which no one will have heard of anyway) and the sordid details about why it went south. You can supply details in in-person interviews if you want, but you won't need to. "I built some really cool technology but I found out my cofounder was playing games with the equity and things fell apart" is probably all that any prospective employer will need or want to know.