Custom Tumblr theme wont save because of non-https urls?

Just had the same problem. Tumblr updated their Encryption policies.

If you’re a theme developer and you’d like to ensure your themes support HTTPS, make sure that any externally hosted resources, such as Cascading Style Sheets (CSS) or Javascript files, and even images, are served using HTTPS.

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As we now know that Tumblr requires that we use HTTPS instead of HTTP, here’s how can we solve the error:

1. Make sure that you are in the customize section and access “Edit HTML”:

2. In the “Edit HTML”, press Ctrl+F (or press the Settings button and then “Find and replace”):

3. Search for “http” and Replace with “https” – apply that to all.

4. As the previous step can cause some links to be “httpss”, this needs to be fixed. By accessing the Find and Replace and Search for “httpss” and Replace with “https”.

The steps bellow should solve your problem. If they don’t, see “Extra considerations” below, more specifically, point 1.

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Extra considerations

1. I’ve done all the above, but it didn’t solve my problem. What should I do?

When one has android-app://, for example:

<link rel="alternate" href="android-app://com.tumblr/tumblr/x-callback-url/blog?blogName=goncalomperes" />

One will need to add [https], as following:

<link rel="alternate" href="android-app:https://com.tumblr/tumblr/x-callback-url/blog?blogName=goncalomperes" />

As @mchid suggested in the comment, apart from android-app://, we will also need to do the above for: "//, ios-app://, and http-equiv.

2. Accordingly to Tumblr support:

Yet another update: SSL is now being turned on by default for ALL Tumblrs that use our Official theme on the web. Even though we don’t recommend it, you can still turn it off in your blog settings.

So changing the Encryption section to allow SSL should not be the problem.