Best Free Postman & SoapUI Alternative — Online REST and SOAP Client (No Install)

Why Developers Are Switching to Browser-Based API Testing
If you've ever needed to quickly test an API endpoint, you know the pain: download Postman (500MB+), create an account, wait for updates, manage workspaces... all just to send a simple GET request.
What if you could test any REST or SOAP API instantly — right in your browser?
That's exactly what SUDTCore's REST Web Client and SOAP Web Client deliver. Zero downloads. Zero sign-ups. Just open the URL and start testing.
The Problem with Desktop API Clients
Postman
Postman is powerful, but it comes with significant overhead:
- 500MB+ download — heavier than most IDEs
- Mandatory sign-in — can't even use it without creating an account
- Electron-based — consumes 300-500MB RAM just sitting idle
- Feature bloat — monitors, flows, environments... most developers just want to send a request
- Paid features — collaboration and advanced features require a subscription
SoapUI
For SOAP testing, the situation is worse:
- Requires Java Runtime — another dependency to manage
- 200MB+ download — and a slow, dated UI
- Steep learning curve — complex interface for simple SOAP calls
- SmartBear upselling — constant prompts to upgrade to the paid version
Insomnia & Thunder Client
- Insomnia recently added mandatory cloud sync and account requirements
- Thunder Client is VS Code-only — not available outside the editor
The SUDTCore Solution: API Testing in Your Browser
🚀 REST Web Client — Postman Alternative
Our REST Web Client provides everything you need for REST API testing:
Full HTTP Method Support
- GET, POST, PUT, PATCH, DELETE, HEAD, OPTIONS
- Custom headers with enable/disable toggles
- Request body with JSON, XML, and plain text format switching
Smart Features
- 🔄 CORS Proxy — Test any API without browser restrictions
- 💾 Save & Organize — Collections with organizations and projects (like Postman)
- 📊 Response Inspector — Status codes, timing, headers, and formatted body
- 🔒 Security — Requests proxied through secure cloud backend; responses are never stored
Who is it for?
- Frontend developers testing backend APIs
- QA engineers validating endpoints
- Backend developers debugging their services
- Students learning about REST APIs
- Anyone who needs to quickly test an HTTP endpoint
📜 SOAP Web Client — SoapUI Alternative
Our SOAP Web Client is purpose-built for enterprise SOAP testing:
Enterprise-Ready Features
- Custom SOAP XML envelope editor
- Dedicated SOAPAction header field
- Support for SOAP 1.1 and 1.2
- Full XML response viewer with headers
Perfect for:
- Enterprise developers working with financial APIs (banking, payments)
- Integration engineers connecting to legacy systems
- Healthcare developers working with HL7/FHIR SOAP services
- Government systems that mandate SOAP/XML protocols
Feature Comparison
| Feature | SUDTCore | Postman | SoapUI | Insomnia | |---------|----------|---------|--------|----------| | Price | Free | Freemium | Freemium | Freemium | | Installation | None | 500MB+ | 200MB+ | 200MB+ | | Sign-up Required | No | Yes | No | Yes | | REST Support | ✅ | ✅ | ✅ | ✅ | | SOAP Support | ✅ | ❌ | ✅ | ❌ | | JSON Body | ✅ | ✅ | ✅ | ✅ | | XML Body | ✅ | ✅ | ✅ | ✅ | | CORS Proxy | ✅ Built-in | ❌ | N/A | ❌ | | Save Collections | ✅ | ✅ | ✅ | ✅ | | Cross-device Sync | ✅ (with login) | ✅ (paid) | ❌ | ✅ (paid) | | Works on Mobile | ✅ | ❌ | ❌ | ❌ | | Response Storage | Never | Cloud | Local | Cloud |
Security & Privacy
One of our core principles: we never store API responses.
When you use SUDTCore's REST or SOAP client:
- Your request is routed through our secure cloud proxy server
- The proxy forwards your request to the target API and returns the response
- The response exists only in your browser session — it's never logged, stored, or cached on our servers
- When you save a request to a collection, only the URL, method, headers, and body template are stored — never any response data
This makes SUDTCore ideal for testing APIs that handle sensitive data — financial endpoints, healthcare APIs, authentication services, and more.
How to Get Started
Testing a REST API
- Go to SUDTCore REST Client
- Select your HTTP method (GET, POST, etc.)
- Enter the API URL
- Add headers if needed (Authorization, Content-Type, etc.)
- For POST/PUT, switch body format (JSON/XML/Text) and enter your payload
- Click Send — view the response instantly
- Click Save to store the request in a collection for later
Testing a SOAP Service
- Go to SUDTCore SOAP Client
- Enter the WSDL/endpoint URL
- Set the SOAPAction header value
- Paste or write your SOAP XML envelope
- Click Invoke Service — view the XML response
- Click Save to store the envelope for reuse
When to Use SUDTCore vs. Postman
Use SUDTCore when:
- You need to quickly test an endpoint without installing anything
- You're on a shared/restricted computer (library, office, client site)
- You want to test from a tablet or phone
- You need CORS bypass without browser extensions
- You're working with SOAP services and don't want to install SoapUI
- Privacy is critical and you don't want responses stored in the cloud
Use Postman when:
- You need advanced features like test scripts, newman CLI, or mock servers
- Your entire team is already on Postman's paid plan
- You need environment variable management across large projects
Try It Now
Stop downloading software just to send an HTTP request. SUDTCore's API clients are free, instant, and secure.
👉 Open REST Web Client — Test REST APIs now
👉 Open SOAP Web Client — Test SOAP services now
No sign-up. No installation. Just open and test.
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