February 7, 2013
How to edit 2013 Seattle and Oslo Master pages
SharePoint 2013 has a fancy new system called Design Manager that is there to help making pages from scratch much easier than in SP2010. However if all you want to do is modify the Seattle or Oslo default master pages and, say, add a footer then all the Design Manage seems to do is obscure what should be a simple process. But it is possible to edit these master pages! Here is how...
1) You must have Design Manager enabled. To do this make sure you enable 'SharePoint Server Publishing' & 'SharePoint Server Publishing Infrastructure' features in both the Site Collection & Site Features.
If like me you get errors and cant enable these features in the browser then try these command lines:
Enable-SPFeature -Identity PublishingSite -URL http://siteurl -Force
Enable-SPFeature -Identity PublishingWeb -URL http://siteurl -Force
2) In your site open: Site Settings > Master pages and page layouts.
3) Find seattle.html and open "Edit properties".
4) Uncheck "Associate File".
SharePoint should now allow you to edit the master file directly without throwing errors.
If you are including your own .css file make sure the path is correct, from trial-and-error it looks like SharePoint will not render the tag if it cant find the file, so it will give the impression that you are unable to save the .html file. ie: look like the above instructions have not worked.
<SharePoint:CssRegistration Name="/Style Library/blah.css" runat="server" />
If you find this helpful please share a comment. Thanks!