Top Alternatives to GNOME Builder

Notepad++ is a free open source notepad replacement and code editor with nice features. It supports syntax highlighting for many languages and has an extension system as well.

Sublime Text is a code editor and syntax highlighter with advanced features which can be enhanced with extensions too.

Eclipse is a free and open source IDE - Integrated Development Platform.

Vim is an open source advanced text editor.

Microsoft Visual Studio is an Integrated Development Environment (IDE) from Microsoft Corporation.

NetBeans is Integrated Development Environment (IDE) for developing complex applications.

Atom is a free open-source code editor from Github.

gedit is a free and open-source code editor.

Geany is a text editor using the GTK+ toolkit with basic features of an integrated development environment.

Aptana Studio is a free open-source web development IDE

Brackets is an open-source editor written in HTML, CSS, and JavaScript with a primary focus on web development.

GNU Emacs is the most popular and most ported Emacs text editor.

Code::Blocks is a free, open-source, cross-platform C, C++ and Fortran IDE built to meet the most demanding needs of its users.

Komodo Edit is a free text editor for dynamic programming languages.

Visual Studio Code is a source code editor developed by Microsoft for Windows, Linux and macOS.

GNU nano is a text editor for Unix-like computing systems or operating environments using a command line interface.

TextWrangler is an all-purpose text and code editor for Mac OS X, based on the same award-winning technology as BBEdit.

Xcode is a complete developer toolset for creating apps for Mac, iPhone, iPad, Apple Watch, and Apple TV.

Bluefish is a free software advanced text editor with a variety of tools for programming in general and the development of dynamic websites.

MonoDevelop (also known as Xamarin Studio) is an open source integrated development environment for Linux, macOS,MonoDevelop on Mac OS X.

VSCodium is an OpenSource repo of Free or Libre Open Source Software Binaries of VSCode.

Qt Creator is a cross-platform C++, JavaScript and QML integrated development environment which is part of the SDK for the Qt GUI Application development framework.

Anjuta is an integrated development environment written for the GNOME project.

B4X is a suite of rapid application development IDEs that allows the creation of applications.

Lime Text is an Open Source, Elegant, and Free Text Editor.