There are a couple of existing Steam ID conversion apps on GameBanana but they are outdated. This application provides the following features:
Validate any format of SteamID
Convert any SteamID format to another (including to the new SteamID3 format)
Convert other IDs in the Steam universe such as Group IDs, chat IDs, etc
Convert profile vanity URLs to SteamID formats
Quickly copy the new SteamIDs by clicking them
2.Known Bugs & Oddities
None at the moment!
Please report additional bugs in the comments of this submission.
3.Possible Frequently Asked Questions
Why is the file size so large? - This tool is built with Electron which bundles a version of Chromium with it. If you don't have a super old HDD then file size shouldn't be a problem.
Why do I get the error "ID could not be converted to the desired format? - Some IDs, such as group IDs, do not have legacy formats and thus cannot be converted to that type.
Download the .7z file and extract it (you will need 7-zip to extract it) to a folder. Then, run SteamIDC.exe.
Windows: 7 or higher Linux: Ubuntu 12.04 or higher, Fedora 21 or higher, Debian 8 or higher Mac: macOS 10.9 or higher
* Linux and Mac versions are currently not provided. These versions will be added if there is a need. This tool was initially made as a test to see what I can do with Electron but I decided to release it here as someone might find it useful.