Migrating Postman Collections to Insomnia: What Works, What Doesn’t, and How to Verify

Problem: Two API Clients, One Collection

Teams that have built extensive Postman collections often switch to Insomnia for its richer scripting, UI, and collaboration features. The question becomes: can we move a large v2.1.0 collection without re‑creating every request?

Thesis: Insomnia’s Import Feature is a One‑Click Bridge, but It Requires a Post‑Import Clean‑Up

Insomnia can read a Postman collection JSON file and auto‑convert requests, headers, body payloads, and environment variables into its native format. The conversion preserves most request details, but advanced Postman features like collection‑level scripts and data files are omitted. Understanding what stays and what falls out lets you plan a smooth migration.

Section 1 – How the Import Works

1. Open Insomnia and click File > Import (or the Import button on the left sidebar).
2. Select Postman Collection v2.1.0 from the list of supported formats.
3. Choose the JSON file you exported from Postman. The file path can be anywhere on your system.
4. Click Import. Insomnia parses the file, creates a new folder named after the collection, and populates it with requests.
5. Any environment objects in the collection become separate environment files in Insomnia’s Environments pane.

During this process, the console panel will log any unsupported items. For example, if the collection contains a dataFile property, you’ll see a warning that data files are not imported.

Section 2 – What Gets Preserved

• Request Method, URL, Query Params, Headers, and Body – These are mapped directly.
• Variables – Postman variable scopes (global, environment, collection) become Insomnia environment files. Variable syntax changes from {{var}} in Postman to the same in Insomnia, so references remain intact.
• Authentication Settings – Basic, OAuth2, and Bearer tokens are converted to Insomnia’s auth fields.
• Request Names & Folders – The folder hierarchy in Postman is replicated.

Section 3 – What Gets Lost or Needs Manual Work

• Collection‑level Scripts – Postman’s event handlers (pre‑request, test) are ignored. Insomnia only supports pre-request and test scripts at the request level.
• Data Files & CSV Imports – If the collection uses dataFile for running tests against CSV rows, the data file is not imported. You’ll need to recreate the data-driven tests manually.
• Postman‑specific Helpers – Scripts that call pm.request or pm.variables will throw errors in Insomnia because those APIs do not exist.
• Large Collections – Importing hundreds of requests can cause a temporary slowdown. If the UI freezes, split the collection into smaller JSON files.
• Variable Name Conflicts – Insomnia has built‑in variables like {{INSOMNIA_URL}}. If the imported collection defines a variable with the same name, it will override the built‑in one. Verify variable scopes after import.

Section 4 – Worked Example: Importing a Simple Collection

Assume you have the following minimal Postman collection JSON (simplified for brevity):

{
  "info": {
    "name": "Sample API",
    "schema": "https://schema.getpostman.com/json/collection/v2.1.0/collection.json"
  },
  "item": [
    {
      "name": "Get Users",
      "request": {
        "method": "GET",
        "header": [],
        "url": {
          "raw": "{{baseUrl}}/users",
          "host": ["{{baseUrl}}"],
          "path": ["users"]
        }
      }
    }
  ],
  "variable": [
    { "key": "baseUrl", "value": "https://api.example.com" }
  ]
}

Steps to import:

1. Save the JSON above as sample-api.json.
2. In Insomnia, click File > Import > Postman Collection v2.1.0.
3. Select sample-api.json and hit Import.
4. Verify that a folder named Sample API appears with a request called Get Users.
5. Open the Get Users request and confirm the URL is {{baseUrl}}/users.
6. Go to Environments and ensure an environment file named Sample API contains the baseUrl variable.
7. Run the request. The response should match the original Postman execution.

All of the above checks are quick to perform and confirm the import succeeded.

Section 5 – Trade‑Offs & Limitations

• Script Compatibility – If your team relies heavily on Postman scripts, you’ll need to rewrite them in Insomnia’s JavaScript environment. This may require learning Insomnia’s insomnia-request API.
• Performance – Importing a 1,000‑request collection can cause a brief freeze. Splitting into smaller files mitigates this.
• Variable Conflicts – Overridden built‑in variables can break requests. Always review the Environments after import.

Actionable Closing – Checklist Before Going Live

1. Run Import – Use the Import button and confirm the console shows no critical errors.
2. Verify Requests – Pick a representative set of requests and compare headers, bodies, and URLs against the Postman version.
3. Test Scripts – Run any pre‑request or test scripts that existed in Postman; rewrite them if they rely on pm helpers.
4. Validate Environments – Open each environment file and ensure variable names are unique and correctly scoped.
5. Performance Check – Open the collection folder and scroll through the requests; if the UI lags, split the collection.
6. Document Differences – Keep a short note of any features that were omitted during import so the team knows what manual work remains.

With these steps, teams can confidently migrate from Postman to Insomnia, preserving the bulk of their API work while addressing the few gaps that require manual attention.