We present SIDE, a Semantic Integrated Development Environment. SIDE uses static analysis to enrich existing IDE features and also adds new features. It augments the way existing compilers find syntactic errors -in real time, as the programmer is writing code without execution -by also finding semantic errors, e.g., arithmetic expressions that may overflow. If it finds an error, it suggests a repair in the form of code-e.g., providing an equivalent yet non-overflowing expression. Repairs are correct by construction. SIDE also enhances code refactoring (by suggesting precise yet general contracts), code review (by answering what-if questions), and code searching (by answering questions like "find all the callers where x < y"). SIDE is built on the top of CodeContracts and the Roslyn CTP. CodeContracts provide a lightweight and programmerfriendly specification language. SIDE uses the abstract interpretation-based CodeContracts static checker (cccheck/Clousot) to obtain a deep semantic understanding of what the program does.