The aim is to prevent avoidable defects and help the people creating a change understand and correct problems before those problems become embedded in an architecture, release, or operational dependency.
Typical examples include security requirements, threat modeling, secure design review, developer guidance, peer review, automated code and dependency checks, and fast testing in development workflows. What moves left should be selected by usefulness and fidelity, not by whether a tool can run early.
Key points
Early decisionsIdentify assets, misuse cases, trust boundaries, privacy needs, dependencies, and security requirements while designs and implementation choices are still inexpensive to change.
Developer feedbackProvide actionable standards, examples, review, and automated checks near the code or configuration change, with clear ownership and routes for exceptions.
Learning loopUse production findings, incidents, penetration tests, and recurring defect data to improve earlier requirements, design patterns, tests, and training.
Important limitationShift-left security does not make late-stage validation, independent review, runtime protection, monitoring, response, or recovery unnecessary. Some behavior and risk appear only in integrated or operational environments, and early checks can be incomplete or wrong.