Are weight values required in an Accept Header with multiple values?

Question

Per the spec, the HTTP Accept header can have multiple values, like so:

Accept: text/html, application/xhtml+xml, application/xml;q=0.9, */*;q=0.8

Source

My question is this: do Accept headers with multiple values need to have at least one weight? Or are they still valid if none of the content types have a weight?

In other words, would this Accept header still be valid according to the spec?

Accept: text/html, application/xhtml+xml, application/xml, */*

Thanks a bunch in advance!

Answer 1

The quality values are optional, but then each entry has an implied quality value of 1.

https://developer.mozilla.org/en-US/docs/Glossary/Quality_values

The importance of a value is marked by the suffix ';q=' immediately followed by a value between 0 and 1 included, with up to three decimal digits, the highest value denoting the highest priority. When not present, the default value is 1.