You can find the DMGs or XIPs for Xcode and other development tools on https://developer.apple.com/download/more/ (requires Apple ID to login).
You must login to have a valid session before downloading anything below.
*(Newest on top. For each minor version (6.3, 5.1, etc.) only the latest revision is kept in the list.)
*With Xcode 12.2, Apple introduces the term “Release Candidate” (RC) which replaces “GM seed” and indicates this version is near final.
Xcode 12
12.4 (requires a Mac with Apple silicon running macOS Big Sur 11 or later, or an Intel-based Mac running macOS Catalina 10.15.4 or later) (Latest as of 27-Jan-2021)
12.3 (requires a Mac with Apple silicon running macOS Big Sur 11 or later, or an Intel-based Mac running macOS Catalina 10.15.4 or later)
12.0.1 (Requires macOS 10.15.4 or later) (Latest as of 24-Sept-2020)
Xcode 11
11.7 (Latest as of Sept 02 2020)
11.4.1 (Requires macOS 10.15.2 or later)
11 (Requires macOS 10.14.4 or later)
Xcode 10 (unsupported for iTunes Connect)
Xcode 9
Xcode 8
Xcode 7
Xcode 6
Even Older Versions (unsupported for iTunes Connect)