How to automatically set a Bearer Token for your Postman requests

I love using Postman but it is a pain having to remember to enter a valid Bearer Token. The following is a Javascript pre-request I’ve used to automate the process.

Background

I’m using Auth0 for auth. My app consists of a Vue.js SPA and a .NET Core API.

Pretty much every endpoint in my API requires authentication. As I write each endpoint in my API I’m writing a Postman request so I can test it.

I have a Postman request to Auth0 to request a token.

To date I’ve been manually entering that token whenever I wanted to use an API endpoint. As you can imagine, this isn’t effective.

I just want my requests to always use a valid bearer token!

My tests under a collection

Step 1 - Create some variables

We to create two variables:

  1. Current bearer token
  2. Expiry date of the above token

You need to think about the scope of the variables. They can be anywhere from a global (across any test you’ve got) to the individual test. Checkout this article about scope in Postman.

I’m choosing to create my variables relative to the collection.

  • Went to Ben’s API
  • Clicked the three dots to open the menu
  • Clicked Edit
  • Let’s jump straight into the Variables tab and create our two variables which I’ve called currentAccessToken and accessTokenExpiry

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Step 2 - the Pre-request Script

I went into Pre-request Scripts and wrote a script that does one of three things:

  • If the token or expiry date is missing I get a fresh token and set the value
  • If both variables are set but the expiry date is in the past I get a fresh token
  • If there is a token AND it’s valid (it’s only good for 24 hours) then do nothing

Here’s the code

A few things to note:

  • I put some console.log statements as Postman has a console and logging is always a good thing
  • I did put all my secrets in this script. I’m not crazy about that but Postman doesn’t have a solution for secrets management. I’m going to try and use a test account in Auth0 to mitigate any issues
  • You cannot call another Postman request from a script. That would have been really useful so instead I ended up writing this
  • You could should write some Tests under the test tab to confirm the token is set, it’s valid, etc. I haven’t yet got around to that

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Step 3 - Authorization Setup

In the Authorization tab I set the

  • Type to Bearer Token
  • Token to {{currentAccessToken}}. This is the token we created and set via the pre-request script

Step 4 - Use the token!

For all your API requests do the following

  • Go into the Authorization tab
  • Under Type select Inherit auth from parent

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You’re done!

But wait there’s more - Console and View the variables

In the top right-hand corner there is an eye icon. If you click it you can see the current state of all your variables. You can also click Edit and change the contents.

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In the bottom-left corner is a console from which you can view all the logs you’ve written. I found it useful for debugging.

You can also use it to confirm that the pre-request script runs before each of your individual tests in your collection.

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