A document handed off to developers to ensure that designs are made according to specifications. “Redline” refers to the literal guides, which are often red lines, within a document that communicate exact spacing, margin, etc.

Many teams require redline documents because developers may not have the design programs – nor want to use them – to interpret the intended output of the design.

There are now many tools that help automate this process of creating specs and redline documents, like Zeplin and Avocode.