How to Backup Your Substack

Tim Forsythe

Published: January 4, 2026

Updated: August 20, 2026

Created: August 31, 2026

Tim Forsythe January 4, 2026 How To 5 min 929 Words

#Substack is a global blogging platform with all the requisite social features necessary to make it popular for readers and writers alike. Slimlines is a small, independant MacOS website framework that can be used to create a wide variety of websites and standalone blogs. With the new Substack plugin, it is easy to use Slimlines to create an archival copy of your Substack newsletter. Read on to learn how to download your Substack archive and the Slimlines desktop application, and how to run it (no configuration necessary). The entire process, takes less than a minute.

Demonstration

To demonstrate what a typical converted Substack newsletter looks like, I've converted mine and put it online as an example.

My Substack Archive (using Slimlines)

Here is my original Substack newsletter for comparison..

My Substack

Below is a side-by-side comparison of the main index pages for both Substack on the left, and Slimlines on the right.

Importing Substack

Download Slimlines (1.1 Kb)
Extract the downloaded file ( slimlines_nnn.zip ) into any folder. It will create a subfolder ( /slimlines ).
Go to the Dashboard Settings on your Substack website, select Import/Export and click on New Export. Within a few minutes your export should be ready. Download it.

Extract your Substack export file directly into the /slimlines subfolder. You should now have /slimlines/posts.csv, /slimlines/email_list.nnn.csv and a /slimlines/posts subfolder.
Run the application ( /slimlines/substack.command ).
If you get an error indicating that "Apple could not verify “slimlines” is free of malware that may harm your Mac or compromise your privacy", you can do the following to disable the alert and run the program.
1. Try to open the app once so macOS logs it into your system.
2. Click Done when the warning box appears.
3. Go to the Apple menu and select System Settings.
4. Click on Privacy & Security in the side list.
5. Scroll down to the bottom Security area.
6. Find the notice that your file was blocked and click Open Anyway.
7. Type your Mac login password to confirm.
It should work from now on.
View your Substack archive in your default browser ( /slimlines/open.html ).

Substack Issues

Not all Substack features are supported. Embedded widgets to Subscribe, Join the Chat, Send a Message, Install Substack, Leave a Comment, Refer a Writer, Start a Poll and Link to Survey, are not supported and will be seemlessly removed from your standalone blog pages. Other embedded widgets to Insert Audio, Insert Video, insert a Financial Chart and insert LaTeX do not include the relevant links necessary to include them, so they will be removed as well. Similarily, social interactions, such as likes, restacks and comments are not directly supported. If you want to add some of these features, the Slimlines distribution includes additional plugins for simple text searching, page likes and support for Disqus comments. To add these and other useful online features to your Substack blog, add the following to the top of the database configuration file ( /slimlines/db.xml ). Note: the disqus plugin requires additional configuration changes. Consult the plugin files ( /slimlines/plugins/disqus/plugin.xml ) for instructions.

<Plugin> plugins\text.search </Plugin>
<Plugin> plugins\page.likes  </Plugin>
<Plugin> plugins\disqus      </Plugin>

Fixing Author Names

The Substack engineering team did not include author name(s) in the exported blog index. Slimlines gets around this by extracting them from post digests when available, unfortunately, not all posts will be internally linked within your newsletter. Slimlines supports a couple of workarounds.

The first method uses Slimlines configuration to add missing parameters such as author name(s), hashtags and categories. To make use of this feature, you will need the Page ID of the post you wish to modify. Page IDs are shown in the build log when you run the application. You can add the following to your /slimlines/substack.xml file, save it and the rerun the build command to update your blog. Since page ids never change, you'll only need to make this change once. It will be reapplied whenever you rebuild your blog. For additional configuration options see <Page>.

<Page> 
  <Id>       Pnnnnnnn       </Id>
  <Author>   Bob Bobson     </Author>
  <Category> Stories        </Category>
  <Hashtags> Fiction, Story </Hashtags>
</Page>

Fixing Cover Images

There is a bug in the export concerning cover images. If you changed the cover image for a post after publication, the exported file will continue to use your original images. Slimlines supports a workaround.

The Slimlines configuration supports overriding the default cover image using the Media configuration. To make use of this feature, you will need the Media ID of the post you wish to modify. Media IDs are shown in the build log when you run the application. You will also need the a link to the updated cover image. You can get this from your Substack website by examining the page source. You can add the following to your /slimlines/substack.xml file, save it and the rerun the build command to update your blog. Since media ids never change, you'll only need to make this change once. It will be reapplied whenever you rebuild your blog. For additional configuration options see <Media>.

<Media> 
  <Id>         Mnnnnnnn      </Id>
  <Substack>   image.png     </Substack>
</Media>

Online Hosting

If you want to host your newly created Substack archive on the web (for free), checkout the following article for simple instructions on setting up a web server and building your database. You'll use the Substack database build file ( /slimlines/substack-db.command ) instead of the one suggested in the article.