Google’s Gary Illyes recommends keeping redirects for at least one year to ensure that ranking signals are delivered permanently.
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Although Google previously recommended keeping redirect activity for a year or more, this is more of a general best practice than something known to directly affect ranking signals.
We now know that site owners can delete the redirect after a year, and Google will continue to send signals indefinitely.
This is Google’s first “specific” answer on how long the redirection needs to stay in order to permanently transmit the signal.
hands up if you asked us recently for how long you should keep redirects in place!
i have a concrete answer now: at least 1 year.
(but try keeping them indefinitely if you can for your users).
— Gary 鯨理／경리 Illyes (@methode) July 21, 2021
In reply to the initial tweet, Illyes answered a series of questions in which he clarified: Yes, when the signal is passed from one URL to another, it will always remain in this state.
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It takes about a year for Google to resend all signals, so this is the recommended minimum time for redirects to remain active.
However, if possible, keep redirects for as long as possible, as this is good for the user experience.
Source: Google help document