Attach Any File to a Substack Post

Comic book file types to the rescue! This requires a small amount of work: compressing, renaming, decompressing. But if you want to attach an unsupported file to your post, you can use this trick.

Last time, Taylor Swift and I demonstrated the embeds you can use in Substack posts.

Back to These Embeds (Swiftie's Version)

In addition to particular URLs, images, and GIFs, Substack allows embeds of a few file types: PDF, XLSX, and the comics file types CBZ and CBR.

What are CBZ and CBR? I didn’t know; do you?

🤔

Time’s up.

They’re ZIP and RAR files.

A ZIP or RAR file can contain compressed¹ versions of essentially any other files: TXT, DOCX, PPTX, MP4, etc. (You can even pack other ZIP and RAR files in them. I’ve seen it.)

ZIP files are more common than RAR files. If you’re unfamiliar with ZIP files, or think your readers will be unfamiliar, you might want to stop here, since this technique requires some comfort with ZIP files.² Or, if you’re still interested, you might want a paid subscription, since I’m offering unofficial but useful Substack support.

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CBZ and CBR files usually contain comic books. (“CB” stands for “comic books.”) Image files named in page number order (001.png, 002.png, etc.) are compressed into one CBZ or CBR file. (“Z” and “R” stand for “ZIP” and “RAR.”)

You can put the CBZ or CBR file into a comics reader application, which will display the images for you in the proper order.

Or … you can decompress (aka unzip or extract) the CBZ or CBR file and then access the images or whatever other files are there.

Or … you might be able to access these files while they are still compressed .

Another “or”? Sure, why not. Or … if the ZIP file is a fake – just another file, like a DOCX, renamed as a ZIP – you can just replace “.zip” at the end with the original file type (like “.docx”) and then view it. This might not work for all file types, so I wouldn’t recommend it except to users willing to experiment.

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To make a long story short, the newsletter creator would:

• use a ZIP application to pack files into a ZIP file

• rename the file from “.zip” to “.cbz”

• drag the CBZ file into the Substack editor to create an embed

• publish the post

The recipient would:

• download the CBZ file (rather than open it in a comics reader)

• rename it from “.cbz” to “.zip”

• extract the contents

• access the contents

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That’s basically it. Now you can send, and others can receive, any kind of file, as long as you and the recipients are comfortable with this technique.

Sure, you could always post the file and make it public on Google Drive, Dropbox, etc. You wouldn’t have to go through compressing, renaming, or decompressing. But maybe you’d prefer attaching a file to the email and web versions of the newsletter.

One reason to do this might be file size. I was able to attach a CBZ file of over 100 MB. I didn’t get the error message that the post was too long for email, and was able to email it successfully to a Gmail address. And it was also downloadable from the web version.

Next time, I’ll try attaching a 1 GB file. 😮 (I wouldn’t recommend attaching such a large CBZ file in real life, unless you warn your recipients. Also, Substack in theory could impose a limit on CBZ or other attachment sizes. And some email services might limit the size of received messages.)

Anyway, try this technique if you’re intrigued, and see what you think.

1. Rather than something by Taylor Swift, I will embed the video of Encanto’s “Surface Pressure” by Luisa Madrigal (Jessica Darrow) here. Surface Pressure —> compressed files —> get it? 🙄😉

2. Since ZIP files and tools are more common, I'm assuming that most publishers who try this technique will use ZIP/CBZ files rather than RAR/CBR files.