Compared honestly · updated 2026-09-26
Thunder Client took collections out of the free tier. CallFlow keeps your requests in files you own.
Thunder Client is the most installed REST client for VS Code, with 7.5 million installs, and it is rated 2.39 stars. The rating tracks a sequence of changes: companies barred from the free version in 2023, the free tier cut to three collections and no environments in February 2025, collections removed from free entirely in August 2025, and a $3 to $16 per user per month price list. CallFlow is the boring alternative: the client is free, the files are yours, and the paid part is a debugger, not your own collections.
- Thunder Client: proprietary storage, free tier now without collections or environments, non-commercial only, $3–16 per user per month for the rest.
- CallFlow: requests are .http files in your workspace (REST Client compatible), collections, environments, history and imports are free forever; Pro ($20, once) is an HTTP debugger, not a toll on your own data.
- Neither is open source. CallFlow makes no network requests of its own and has no account; Thunder Client's paid tiers require login and its docs say offline activation is Enterprise-only.
Thunder Client vs CallFlow, side by side
| Thunder Client | CallFlow | |
|---|---|---|
| Price | Free (non-commercial, limited); Starter $3, Business $7, Enterprise $16 per user/month, billed annually | Free; Pro $20 one-time |
| Account required | Free: not required per the docs; paid tiers: login required | Never |
| Collections on the free tier | Removed 3 August 2025 | Unlimited, as files in your workspace |
| Environments on the free tier | 0 | Unlimited, secrets kept in VS Code's secret storage |
| Commercial use of the free tier | Not allowed since October 2023 | Allowed |
| Where your data lives | Proprietary JSON in the extension's storage (git sync on paid tiers) | Plain .http files, REST Client compatible, next to your code |
| Export of your own requests | Reviews in 2026 report export blocked on the free tier | Always: files, cURL, HAR |
| Works in Cursor, VSCodium, Windsurf | Free tier VS Code only since February 2025 | Yes, via Open VSX |
| HTTP traffic capture / debugger | No | Pro: capture from terminals and debug sessions, inspect, save as request, replay |
| Scripting and tests | Paid tiers | v0.2 Pro |
| Marketplace rating (26 Sep 2026) | 2.39 stars, 752 ratings | New |
Competitor facts were checked on 2026-09-26 against the sources linked below. If something has changed, tell us and we will correct it.
Where Thunder Client users get hurt
The free tier was cut three times
October 2023: the maintainer wrote that "companies are not allowed to use the free version." November 2024: the announced free tier became three collections, fifteen requests per collection, no environments, no OAuth2, and from February 2025 VS Code only. July 2025, release notes for 2.36.0: "The free version will no longer support collections starting August 3rd, 2025. A paid plan will be required."
"You built this extension for the community. You gave us the terms, we used it and now you are changing the terms as you please and locking us out without any notice." — support discussion, November 2024
Sources: Discussion #1365 (Oct 2023) · Discussion #1648, changes to the free version · Release 2.36.0 · Pricing
Your past requests behind a paywall
"You must pay to look at a request you did in the past... Predatory at best. I'll pay for a good tool, but don't string me along, then pull the rug out." — Marketplace review, May 2026
"used it a couple of years. Now it does not even allow you to export your own files. Most important features are behind the paywall." — Marketplace review, April 2026
CallFlow's rule is the opposite: the exit door is never gated. Your requests are files; export is free forever.
Sources: Marketplace listing and reviews · Issue #1683, locked out under the limits
The free fallback has gone quiet
The other 7.6-million-install option, REST Client, has had no release since August 2022; by August 2026 a fork was announced because "61 pull requests are waiting." CallFlow reads and writes the same .http format, so a REST Client collection opens in CallFlow unchanged, and vice versa.
Sources: REST Client issue #1449
What CallFlow does instead
CallFlow keeps every request as a block in an .http file under .callflow/ in your workspace: method, URL, headers, body, in the format REST Client has read since 2016. Collections are folders. Environments are a JSON file with secrets held in VS Code's secret storage. History keeps your sends with full bodies. Import from cURL, Thunder Client, Postman and HAR; export cURL and HAR. All of that is free for anyone, at work or not.
Pro is $20 once and buys a different thing: an HTTP debugger. Start capture and every terminal and debug session in the workspace routes through a local proxy on 127.0.0.1 with a CA generated on your machine. Inspect what your code really sent, turn a captured call into a saved request, replay it. No account, no server, no telemetry, and the licence check is offline.
To be fair to Thunder Client
Thunder Client has years of polish, a larger feature set today (scripting, test suites, GraphQL, team git sync), and a paid tier that fits companies which want a vendor relationship. If your team already pays for it and the workflow fits, there is no reason to move. CallFlow is narrower on purpose and new; its full-page differentiators are the file format, the free tier's terms, and the debugger.
Try CallFlow
Free on the Visual Studio Marketplace (Open VSX coming soon). No account, no server, no telemetry. CallFlow Pro is a $20 one-time purchase, sold through Paddle, and your files and exports are never paywalled.
Install from the Visual Studio Marketplace Read how CallFlow works
Questions people ask
- Can I import my Thunder Client collections?
- Yes. Export a collection from Thunder Client as JSON (available while your plan allows export) and use CallFlow: Import. Folders, headers, bodies, auth and variables are converted into .http files.
- Is CallFlow's free tier really free for commercial use?
- Yes. There is no commercial restriction on the free features, and the EULA says so.
- Does CallFlow need an account for Pro?
- No. The Pro licence is a key you paste in, verified offline, valid on any machine you use.
- What is in Pro exactly?
- Capture from terminals, debug sessions and a launched browser; the inspector; save-as-request; replay and edit-replay; HAR export of captures; history up to 20,000 entries. Scripting, tests and a collection runner come in 0.2.