Blog Perfectly sizing images in your API documentation

Perfectly sizing images in your API documentation

Images are cool and they should be everywhere in your API doc. End of this blog post, thanks everyone!

Well, more seriously, many people, obviously including me, love a nice visual, especially when it comes to learning something new like, let’s say… how to use a new API. always supported the ability to add images in the markdown of your API documentation and has now extended it with the ability of sizing to your needs.

Whether you want to have your API documentation more lively to your users with gifs, share your API diagrams, illustrate complex API behaviors (like polymorphism) with a nice visual, and you have an API Contract based on OpenAPI or AsyncAPI, you can now make sure the images in your API documentation renders in the size you’d prefer them to.

How renders images by default

Usually, in markdown, you would use this syntax to add an image

![Alt text](/path/to/image.jpg "Image title")

By default lets the browser decide how it will display the generated html <img src="image.url">. For instance if the image is in a table cell, it will be limited to the size of the table cell, if in a paragraph, it will use the default image size.

However, you can now decide on the image size yourself.

How to customize the image size in your API documentation

Now you can take it a step even further into the personalisation with a =dimension parameter that lets you manually decide how your image should be displayed in your documentation.

=dimension just extends the well known Markdown syntax by allowing you to give extra dimension information before the closing parenthesis

![Alt text](/path/to/image.jpg "Image title" =dimension)

As an example, if you wanted to display an image of 100 pixels height and 50 pixels width you could write

![Alt text](/path/to/image.jpg "Image title" =100pxx50px)

=dimension uses the following syntax =[width][unit]x[height][unit] and is itself completely optional as well as almost all its parameters: just width or x + height are mandatory. If you don't specify width or height, the other value will be a ratio calculated from the original size of the image so it doesn't shrink.

Telling this might be confusing so here are a few examples to better understand what you can do with this =dimension parameter:

Let’s take this SpongeBob plushie picture. See how it renders by default:

SpongeBob plushie image in a documentation

And now let’s play around with the =dimension parameter!

=100pxx50px   # with everything
=100x50     # without unit

SpongeBob plushie image in a documentation with 150 x 50 px sizing

=100        # without height (x separator not needed) and unit
=100px      # without height

SpongeBob plushie image in a documentation with 100px sizing

=x50        # without width and unit
=x50px      # without width

SpongeBob plushie image in a documentation with 100px sizing

Note that not specifying an unit will fall back to pixel.

It also supports all CSS length units, so you can work with px for pixel, %, or any other absolute or relative unit you are used to.

Same image as above with =dimensionset to =200cm: SpongeBob plushie image in a documentation with 200cm sizing

Always make sure how the property you use is handled by different browsers as it may differ.

You can find an extended description of the behavior of this new image sizing feature in the documentation.

Trying with your own API documentation lets you preview how your documentation would look like by simply uploading your API Contract in the preview tool.

You can also preview how your images will render while editing your API contract or in your tests using the CLI with the command

npm install -g bump-cli   ## installs cli

bump preview --live --open openapi-definition.json

Option --open will open the preview in your default browser, and --live will automatically update the preview in your browser upon saving edits in the file.

And do you know what’s best? You don’t even need a account to use our preview, so enjoy playing around with images to see how your API documentation could render with perfectly sized images 🖼️!


Images are cool and they should be everywhere in your API doc.

Images Everywhere meme

Valériane Venance is Principal Developer Advocate at She loves writing docs and articles. You can follow her on Twitter or connect on LinkedIn

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