Glossary

Shift left

Shift left means moving a verification activity earlier in the delivery process so problems are found while they are still cheap to fix.

Short answer

What is shift left?

Shift left means moving a verification activity earlier in the delivery process so problems are found while they are still cheap to fix.

Explained two ways

Plain and technical

In plain terms

Instead of testing security or quality at the end, you check it as the code is being written, when changing it costs almost nothing.

Technically

Shifting a check earlier only produces value if the resulting feedback is fast, scoped to the change rather than the whole codebase, specific enough to act on, and accurate enough to trust. A check that reports a repository entire backlog on every pull request is ignored within a week, regardless of how early it runs.

Example

What it looks like in practice

A dependency scan runs on a pull request and reports only what that change introduced (one package and the version to upgrade to), rather than the 400 pre-existing findings in the repository.
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More definitions

See these concepts in a running system

A 30-minute walkthrough against your own infrastructure rather than a slide about the theory.