Notes from the Google Webmaster Hangout on the 5th of October 2018.
Hreflang is a Minor Canonicalization Signal
Google uses hreflang as a small signal when picking the canonical version of a page, but this needs to be backed up by consistent signals provided by rel canonicals, internal linking and sitemap files.
Check Alt Text is Present on Mobile Version of Images
John recommends checking that the alt text is present for the mobile version of images for mobile-first indexing. This is something Google has seen missing from sites that serve different content on mobile.
Image Aspect Ratio Important For Some Types of Structured Data
Image aspect ratio can be important for some types of structured data and rich results like recipes. John recommends following Google’s suggested image aspect ratio and minimal size.
Submit Reconsideration Requests Separately For Different Subdomains
Submit reconsideration requests separately if manual actions have been received for different subdomains, and make sure the disavow files are updated for each one.
Update Last Modified Date in Sitemap & Use Validate Fix in GSC to Get Pages Crawled Sooner
If technical issues cause pages to show incorrectly (e.g. serving a blank page), you can get Googlebot to crawl these sooner by submitting sitemap files with the last modification date set to when the affected pages were restored. You can also click ‘validate fix’ on pages with errors in Search Console to get Googlebot to recrawl these pages faster.