What Does it Mean?
The x-robots tag is an area in the HTTP response header that tells search engines and other crawlers how to treat content found on the URL. In this way, it is very similar to the meta robots tag, but the difference is that this information is found in the HTTP response header instead of the page source.
A typical X-Robots-Tag:
Similar to the meta robots tag, the x-robots tag can contain multiple values, comma-separated. The most common values include:
all: No restrictions for robots. This is the default value, so it is not actually needed to be written explicitly.
index: Instructs search engines to index the page content. This is the default behavior, so is not really needed.
noindex: Instructs search engines not to include the page in the search engine's index.
follow: Instructs search engines to follow all links on the page as normal. Again, this is the default behavior, so is not really needed.
nofollow: Instructs search engines not to follow the links on the page.
none: Equivalent to “noindex, nofollow”.
Why It's Important
Any URL that has the value of noindex in the X-Robots-Tag will not be indexed by search engines. These URLs will not be accessible to users via organic searches (for example in an image search).
If this is the intention, then there’s no problem to fix. But if you want this image to rank in an image search, you’ll have no chance of ranking until this tag is removed or modified.
How To Fix
If this URL should be excluded from search engines' index, nothing needs to be done. However, if this URL should be included in search engines' index, remove the X-Robots-Tag or remove the noindex or none directive.