HTTP Debugger Pro is Fiddler alternative software for developers and QA teams on Windows, built as a native application. Unlike Fiddler, it does not run a local proxy and does not change your Windows proxy settings. HTTP Debugger Pro captures traffic system-wide, from every process on the machine. The installer is just 12.6 MB and requires no .NET runtime and no Electron bundle.
Fiddler Classic and Fiddler Everywhere: which is which
Progress ships two separate Fiddler products, and a search for "Fiddler" can land on either. Fiddler Classic is the original Windows-only web debugger, still downloadable and now restricted to non-commercial use. Fiddler Everywhere is the current product: it runs on Windows, macOS, and Linux, and it is what Progress points commercial users to.
| Property | Fiddler Classic | Fiddler Everywhere |
|---|---|---|
| Platforms | Windows only | Windows, macOS, Linux |
| Development status | Maintenance mode, with no commitments for releases, patches, or technical support | The product Progress develops and supports |
| Licensed for | Non-commercial use only | Commercial, business, organizational, or revenue-generating use |
| Price | Free | Lite $7, Pro $13, Enterprise $37 per user per month, billed annually |
| Trial | Not applicable | 10 days with every paid feature |
| Official download | Download Fiddler Classic | Download Fiddler Everywhere |
Product facts and tier prices as published by Progress on telerik.com, read on 2026-08-23.
Fiddler Classic stays free under the non-commercial terms above, so a hobby project or an internal tool can keep using it. Paid work moves to a Fiddler Everywhere subscription.
Why use a proxy-less Fiddler alternative on Windows?
Beyond the commercial-use restriction, a proxy-based capture model has technical drawbacks of its own. Fiddler and similar tools capture traffic by running a local proxy and registering it as the Windows system proxy. Some applications ignore that setting entirely and connect straight to the internet — legacy apps, CLI tools, and clients with their own proxy configuration — so their traffic never appears in the capture. Unregistering the proxy on exit is the tool's job, and a crash that skips it leaves the machine with no internet at all.
HTTP Debugger Pro takes a different approach to capturing traffic. It does not run a proxy server on your machine, does not open a listening port, and unlike a proxy-based sniffer it captures those applications too. This approach preserves corporate proxy, PAC, and VPN routing, inspects inbound localhost server requests, and attaches process and connection metadata to each session.
What HTTP Debugger Pro can inspect and change
HTTP Debugger Pro comes with a rich set of tools for inspecting and changing traffic: headers, cookies, bodies, timings, sizes, and process metadata, decrypted HTTPS, and capture of HTTP/1.x, HTTP/2, WebSocket, SSE, and gRPC. Traffic can be searched, filtered, edited, resent, or modified with rules, and sessions saved or exported as reports.
Common HTTP debugging workflows
- Troubleshoot third-party API integrations — see the exact request your code sends and the API's real response.
- Optimize your API and desktop apps — find slow and large calls that browser devtools never see.
- Debug WebSocket, SSE, and gRPC streams — read individual frames, events, and messages.
- Debug AI agents and MCP servers — see what they send and receive on localhost.
- Reproduce edge cases — edit a captured request and resend it, or fake the response with a rule.
- Let an AI assistant read the capture — connect Claude Code or Codex through the built-in MCP server.
HTTP Debugger Pro vs Fiddler Classic
Both tools solve the same problem on Windows, but in different ways:
| Capability | HTTP Debugger Pro | Fiddler Classic |
|---|---|---|
| Capture architecture | Windows service and protocol-level capture | Intercepting HTTP proxy |
| System proxy changes | No changes required | Becomes the system proxy |
| Applications without proxy support | Captured directly | Not captured |
| Corporate proxies and VPNs | Fully compatible | Requires configuration |
| HTTP protocol versions | HTTP/1.x and HTTP/2 | HTTP/1.x only |
| Streaming and RPC protocols | WebSocket, SSE, and gRPC | WebSocket only |
| Built-in MCP server | Yes | — |
| License model | Paid perpetual license | Commercial use not permitted |
| Development status | Actively maintained | Maintenance mode |
For a deeper look at the capture models, read the no-proxy vs proxy HTTP debugging comparison.
No internet after Fiddler: the proxy it left behind
A proxy-based debugger writes its own address into the Windows proxy
settings on start and removes it on exit. An unexpected exit skips the
cleanup: a crash, an OS interruption, a killed process, or an uninstall
while the tool is still registered. The entry survives, every
application that reads the system proxy keeps dialing a loopback
address such as 127.0.0.1:8888 where nothing listens any
more, and the machine looks offline while the network is fine. Progress
documents this as
leaked proxy settings.
Each client words the same failure differently. Chrome and Edge show
Unable to connect to the proxy server with
ERR_PROXY_CONNECTION_FAILED. Firefox says the proxy server
is refusing connections. Command-line tools, services, and SDKs report
that they cannot establish a connection through the proxy. All of them
are reading the same stale setting.
How to fix it in Windows
To fix it, close Fiddler, open
Settings › Network & internet
› Proxy (or run
ms-settings:network-proxy), switch
Use a proxy server off, and restart the browser or
application. If your network really uses a proxy, put its address back
instead of clearing the field.
Why this cannot happen with HTTP Debugger Pro
HTTP Debugger Pro captures at the protocol-filter level instead of terminating connections in a local proxy. It never registers itself as the system proxy, never opens a listening port for clients to target, and leaves the Windows proxy settings untouched. Stop it, crash it, or uninstall it and connectivity is unaffected: nothing was rerouted in the first place.
The one thing it installs is a local root certificate. Any tool that reads HTTPS has to install one: without a trusted local root the traffic stays encrypted. HTTPS inspection stays off until you enable it, and the certificate setup guide covers trusting that root in Windows, Firefox, and Java.
Perpetual license vs subscription
HTTP Debugger Pro is sold under a perpetual license. The current published price is $129 per seat before volume discounts, paid once for continued use of the purchased version. Current volume tiers apply 10% for 5–9 seats, 15% for 10–24 seats, 20% for 25–49 seats, 25% for 50–99 seats, and 30% for 100 or more seats.
Fiddler Everywhere uses a subscription license. According to the Fiddler Everywhere EULA, an active subscription is required to continue using the product, subscriptions renew automatically unless auto-renewal is disabled, and access ends when the subscription ends.
| Seats | HTTP Debugger, 3 years, no renewals | HTTP Debugger with renewals, 3 years | Fiddler Everywhere, 3 years |
|---|---|---|---|
| 1 | $129 | $307 | $468 |
| 5 (10% off) | $581 | $1,382 | $2,340 |
| 20 (15% off) | $2,193 | $5,219 | $9,360 |
| 50 (25% off) | $4,838 | $11,513 | $23,400 |
An HTTP Debugger Pro license includes one year of updates; the renewals column adds a $89 renewal per seat for each remaining year, at the same volume discount. Fiddler Everywhere Pro at $13 per user per month billed annually, the tier comparable to HTTP Debugger Pro. Based on public prices verified on 2026-08-23.
Move your Fiddler Classic rules and sessions across
Switching tools normally means rebuilding every rule by hand. Version 10.8 added an import for both halves of that work, in two entries of the Export/Import menu.
Saved sessions: SAZ and HAR
Import From SAZ reads unencrypted Fiddler Classic
archives and Import From HAR reads HAR 1.1 and 1.2
files, so a capture taken in Fiddler Classic or exported from browser
developer tools opens in the same grid as a live session. Load Session
accepts .saz and .har directly. The imported
sessions replace the current capture after the confirmation Load
Session already uses. One import takes up to 32 files, 10 000 sessions
per file, and 512 MB per archive.
Not imported: encrypted SAZ archives, Fiddler Classic WebSocket payloads, gRPC entries, sessions missing either the request or the response, non-HTTP(S) schemes, and Fiddler Everywhere data.
Rules and Composer requests
Import From Fiddler reads AutoResponder rules from a
discovered AutoResponder.xml and from the FARX files you
select. FFX filters and Quick Filters come across where an exact HTTP
Debugger equivalent exists. The dialog previews every source with the
number of items it will take. Saved Composer requests arrive as HTTP
Submitter presets, ready to send again.
Imported rules arrive switched off, inside a new profile called
Fiddler Rules, so nothing touches your traffic until you have
read them. Unsupported conditions, unknown actions, and external-file
dependencies are skipped and explained in the import report;
CustomRules.js is never imported. When a Fiddler Classic
installation is on the machine, HTTP Debugger offers the import once in
a message bar after certificate setup.
The import shipped in version 10.8 and runs in the 7-day trial, so a real SAZ archive can be opened before any decision. Seat pricing and volume tiers are on the purchase page.
FAQ: HTTP Debugger Pro vs Fiddler
Is HTTP Debugger Pro a proxy server?
No. HTTP Debugger Pro is not a proxy server and does not set itself as a system proxy. It uses a different approach to capture HTTP/HTTPS traffic, which helps avoid proxy-related network issues and conflicts with corporate proxies or VPN clients.
Can Fiddler and HTTP Debugger Pro run on the same computer?
Yes. Because HTTP Debugger Pro is not a proxy and uses a different capture mechanism, it can run side by side with Fiddler on the same Windows machine.
Is there a perpetual-license alternative to Fiddler Everywhere?
Yes. HTTP Debugger Pro is a perpetual-license alternative to Fiddler Everywhere for Windows. Its current price is $129 per seat before volume discounts, paid once for continued use of the purchased version, with no subscription.
Can I import my Fiddler sessions into HTTP Debugger Pro?
Yes. HTTP Debugger Pro can import HAR 1.1/1.2 files and unencrypted Fiddler Classic SAZ archives with HTTP and HTTPS request-response sessions. It imports supported AutoResponder.xml and FARX rules, plus exact FFX and Quick Filter mappings; rules start disabled in a rules profile of their own. Encrypted SAZ, Classic WebSocket payloads, scripts, and Fiddler Everywhere data are not imported.
Will HTTP Debugger Pro see traffic from applications that do not support proxies?
Yes. Capture does not depend on the application's proxy support — HTTP Debugger Pro reads the traffic of any Windows process, whether it goes through a proxy or straight to the internet.
Does HTTP Debugger Pro work with VPNs and corporate proxies?
Yes. HTTP Debugger Pro can capture traffic over LAN, Wi-Fi, other network adapters, and VPN tunnels, and it can also monitor applications whose traffic is already routed through an upstream or corporate proxy.
What platforms does HTTP Debugger Pro support?
HTTP Debugger Pro is designed for Windows desktops and servers and supports Windows 10 and Windows 11, both 32-bit and 64-bit. There is no macOS or Linux build.