Free Alternative to Charles

Proxyman is the most polished free alternative to Charles and feels like what Charles would be if it were rebuilt from scratch as a native Mac app today. It's built with SwiftUI for a beautiful interface that follows macOS design guidelines, features automatic SSL configuration that works in seconds instead of Charles's multi-step certificate installation, and includes iOS/Android simulator support with auto-detection that eliminates manual proxy configuration. Built with Apple Silicon optimization, it renders network traffic blazingly fast on M1/M2/M3/M4 Macs—opening large session files that make Charles stutter.

The free tier is genuinely generous, not a limited trial—most features including SSL inspection, request/response viewing, filtering, and session export don't require paying. The interface feels more modern than Charles with better syntax highlighting for JSON/XML, collapsible request trees for navigating complex session captures, and instant search across all captured traffic using fuzzy matching. Certificate installation is completely automated with system-level integration, and iOS simulators are detected automatically the moment you launch them without touching simulator network settings.

The Map Local feature (Pro only) lets you replace remote API responses with local files for testing edge cases. Proxyman also supports scripting (Pro) for automating repetitive debugging tasks and breakpoints for intercepting and modifying live traffic as it flows through the proxy. The developer actively ships updates with new features based on community feedback, making it feel like a living product rather than maintenance-mode software.

HTTP Toolkit is a modern, 100% open-source HTTP debugging proxy with a gorgeous UI that makes Charles look dated by comparison. It intercepts HTTP/1, HTTP/2, WebSockets, and HTTPS with one-click setup that automatically configures browsers, Docker containers, and mobile devices. The free version covers most debugging needs, and open-source contributors get Pro features free as a thank-you for their work.

Cross-platform and designed from the ground up for instant, targeted debugging without the complexity of Charles's menu-heavy interface. The interface uses a clean card-based layout that makes it easy to drill down into request details—each request expands to show headers, body, timing, and validation in collapsible sections. Unlike Charles's Java-based UI which can feel sluggish, HTTP Toolkit uses Electron with React for a responsive modern experience with smooth animations and instant search.

The project is actively maintained on GitHub with frequent updates adding new features based on user requests. One standout feature is the automatic body decoding—HTTP Toolkit automatically decompresses gzip, Brotli, and deflate responses so you can read them without manual decompression. The Docker integration is particularly impressive, offering one-click setup that automatically configures containers to route traffic through the proxy without editing Dockerfiles or docker-compose.yml files.

For security researchers, HTTP Toolkit makes it easy to mock endpoints for testing how applications handle errors, timeouts, or malformed responses. The HAR export is comprehensive, preserving all timing data and headers for later analysis or sharing with teammates who don't have HTTP Toolkit installed.

mitmproxy is a powerful open-source proxy used by security researchers and developers worldwide for its unmatched flexibility and scriptability. It supports HTTP/1, HTTP/2, HTTP/3, WebSockets, and any SSL/TLS-protected protocol with man-in-the-middle interception. Python scripting enables automation for testing, security research, and traffic analysis that would be impossible with GUI-only tools.

Available as CLI (mitmproxy for interactive terminal UI), non-interactive (mitmdump for automated scripts), or web UI (mitmweb for visual inspection). The Python API is incredibly powerful—you can write custom scripts that intercept requests based on URL patterns, modify authentication headers, simulate network failures, replay requests with modified payloads, or automatically test API endpoints for vulnerabilities. Security researchers use it for penetration testing and reverse engineering, developers use it for automated API testing in CI/CD pipelines, and QA teams use it for simulating various network conditions.

The transparent proxy mode lets you intercept system-wide traffic without configuring each application individually. The reverse proxy mode is useful for protecting backend services by inspecting all incoming traffic. mitmproxy can export flows to HAR format, curl commands, or httpie format for reproducing requests. The console UI uses vim-style keybindings for efficient navigation—filtering, searching, and inspecting traffic without touching the mouse.

For teams running automated tests, mitmdump can run in CI/CD pipelines to capture all HTTP traffic during test runs and validate request/response formats. The scripting capabilities extend to modifying TLS versions for testing legacy systems, chaining upstream proxies for corporate network environments, and implementing custom authentication flows.

Burp Suite is the industry standard for web application security testing, and the Community Edition provides powerful proxy capabilities for free. While it's designed primarily for security professionals conducting penetration testing, developers can use it for deep HTTP debugging. The proxy component intercepts all traffic between your browser and target applications, allowing detailed inspection and modification of requests and responses.

The Repeater tool lets you manually modify and resend individual HTTP requests for testing edge cases. The Intruder tool (Pro only) automates request modification for fuzzing and brute-force testing. Burp's Decoder helps with encoding/decoding various formats like Base64, URL encoding, and HTML entities.

The Comparer tool visualizes differences between two requests or responses. While the interface is utilitarian rather than beautiful, it's extremely functional for security-oriented workflows. Burp Suite integrates with web browsers through certificate installation and offers detailed request history with powerful search and filtering.

The Community Edition has limitations compared to Pro (no automation, slower Intruder, no scanning), but for manual HTTP debugging and security testing, it's free and powerful. Many security researchers use Burp Suite alongside tools like mitmproxy, using Burp for manual testing and mitmproxy for automated scripting.

OWASP Zed Attack Proxy (ZAP) is one of the world's most popular free security tools, actively maintained by hundreds of volunteers. Like Burp Suite, it's designed for finding security vulnerabilities in web applications, but it's 100% free and open-source. ZAP functions as an intercepting proxy that sits between your browser and web application, capturing all traffic for inspection and modification. The automated scanner crawls your application and reports potential security issues like SQL injection, XSS, and CSRF vulnerabilities.

The Fuzzer sends multiple variants of requests to test how applications handle unexpected input. ZAP includes a traditional spider for discovering content and an Ajax spider for modern JavaScript-heavy applications. For API testing, ZAP can import OpenAPI/Swagger definitions and automatically test endpoints. The interface offers both a traditional Java Swing GUI and a HUD (Heads Up Display) mode that overlays security information directly in your browser. ZAP is particularly strong for security-focused workflows but also works well for general HTTP debugging.

The active community provides regular updates and maintains extensive documentation. ZAP integrates well with CI/CD pipelines through Docker images and command-line tools, making it suitable for automated security testing in DevOps workflows. For developers who need both HTTP debugging and security testing capabilities, ZAP provides exceptional value as a completely free, open-source option.

Requestly takes a different approach to request debugging—instead of being a traditional proxy, it's a browser extension that intercepts and modifies HTTP requests directly in Chrome, Firefox, Edge, and Safari. This means zero proxy configuration, no certificate installation, and instant setup. Create rules to redirect URLs, modify headers, inject scripts, add delays for testing race conditions, or mock API responses without backend changes.

The visual rule builder makes it accessible to developers who find proxy configuration intimidating. Requestly is particularly useful for frontend developers who want to test how their applications handle different API responses without modifying backend code or running local API mocks. The Mock Server feature lets you create fake API endpoints that return specific responses, useful for testing error scenarios.

For teams, Requestly offers cloud sync so rules can be shared across the team. The Session Recording feature captures full HTTP traffic with console logs and network data for debugging production issues. Unlike traditional proxies that require configuring each application, Requestly works immediately for all browser traffic.

The Desktop App extends capabilities beyond browser traffic, working more like a traditional proxy. Requestly bridges the gap between browser DevTools (which can't modify traffic) and full proxies (which require setup). For developers working primarily on web applications who want faster workflows than proxy setup allows, Requestly offers compelling convenience.

Wireshark goes deeper than HTTP—it captures all network traffic at the packet level, decoding hundreds of protocols including TCP, UDP, TLS, DNS, ICMP, and more. Overkill for simple HTTP debugging but essential for understanding complex network issues, diagnosing TCP connection problems, analyzing DNS resolution failures, and troubleshooting connectivity problems that application-level proxies can't reveal. Network engineers use it to diagnose routing issues and bandwidth problems, security teams use it to analyze attack traffic and detect anomalies, and developers use it when application-level debugging isn't revealing the root cause of mysterious failures.

The display filters are incredibly powerful once you learn the syntax—you can filter by IP address, port, protocol, packet size, or custom criteria. The Follow Stream feature reconstructs full TCP conversations from individual packets. Statistics and graphs provide insights into network performance, bandwidth usage, and protocol distribution.

Wireshark can decrypt HTTPS traffic if you provide the server's private key or configure browser key logging. The colorization rules help quickly identify different protocols in packet captures. While the learning curve is steep, Wireshark is invaluable for debugging issues like TCP retransmissions, packet loss, DNS failures, TLS handshake errors, and routing problems that proxies operating at the HTTP level can't see. For developers encountering 'connection reset by peer', timeout errors, or other low-level networking mysteries, Wireshark reveals what's really happening on the wire.

For web development, Chrome/Safari/Firefox DevTools network panels are often enough for HTTP debugging without any extra software. You can see all requests with full headers, timing waterfalls, and response data with zero setup—just press Cmd+Option+I. It's not a proxy so it can't intercept mobile apps or desktop software, but for web-only debugging, it covers most needs.

The Network tab shows complete request/response headers, allows copying requests as cURL or fetch commands for reproducing in other tools, and provides timing waterfall charts showing DNS, connection, TLS, and response times. Modern browsers include network throttling simulation for testing on 3G/4G connections, request blocking for testing error scenarios, and HAR export for sharing network logs with teammates. Chrome DevTools can override responses locally for testing different API responses without backend changes.

The WebSocket inspector shows frame-level traffic for WebSocket connections. Safari's Web Inspector excels at debugging iOS web views through remote debugging. Firefox DevTools includes an excellent request editor for replaying requests with modifications.

For purely web-based debugging without mobile apps or desktop applications, DevTools might be all you need—it's free, always available, and constantly improving with browser updates. The Performance panel integrates network timing with JavaScript execution and rendering for holistic performance analysis.

Fiddler Everywhere is the modern cross-platform version of the classic Windows-only Fiddler proxy tool that's been trusted by developers for nearly two decades. It offers a clean, modern interface for capturing HTTP/HTTPS traffic with automatic certificate setup, request composition for crafting custom requests, and traffic modification through rules. The free tier includes basic debugging features including traffic capture and inspection, while paid plans unlock collaboration, cloud sync, and advanced automation features.

Unlike the original Fiddler Classic which only ran on Windows, Fiddler Everywhere works on macOS, Windows, and Linux with a consistent experience across platforms—important for teams using different operating systems. The AutoResponder feature lets you mock API responses by creating rules that return specific responses for matching requests, useful for testing error scenarios without backend changes. The Composer tool builds custom HTTP requests from scratch for API testing.

Traffic can be filtered by process, host, or custom conditions to focus on relevant requests. Sessions can be saved and shared with teammates for collaborative debugging. The Rules feature automatically modifies traffic based on conditions, similar to Charles's Rewrite or Map Local features.

Fiddler Everywhere offers team collaboration features in paid tiers, letting teams share sessions, rules, and configurations through cloud sync. For organizations migrating from Windows to Mac or needing cross-platform consistency, Fiddler Everywhere provides familiar Fiddler workflows everywhere.

While Postman is primarily known as an API client for testing REST and GraphQL endpoints, it also functions as a lightweight proxy for capturing HTTP traffic. Postman's proxy mode captures requests your applications make, automatically organizing them into collections that can be saved, documented, and shared with team members. This is particularly useful when you want to reverse-engineer an API by capturing actual traffic and then using those captured requests as a foundation for API tests.

The interface is designed for API workflows rather than general network debugging—you won't get packet-level details, but you will get clean request/response organization with excellent JSON/XML formatting. Postman excels at taking captured requests and turning them into repeatable test cases with assertions, environment variables for different deployment stages, and automation scripts using JavaScript. The Collection Runner executes multiple requests in sequence for integration testing.

Mock Servers simulate API endpoints for frontend development before backends are ready. For teams already using Postman for API development, enabling the proxy mode adds traffic capture capabilities without installing another tool. However, dedicated proxies like Proxyman or mitmproxy offer more powerful traffic inspection, filtering, and modification than Postman's proxy feature. Use Postman if your workflow is API-centric and you want to capture traffic specifically for building API test collections.

Insomnia is a lightweight, open-source API client that serves as an alternative to Postman with a simpler, more focused interface. Like Postman, it's primarily an API testing tool but includes proxy capabilities for capturing HTTP traffic from applications. Insomnia shines with its clean, minimal design that avoids the feature bloat some users feel Postman has accumulated.

It supports REST, GraphQL, and gRPC with excellent request organization through workspaces and folders. Environment variables and templating with Nunjucks allow dynamic request generation. The Timeline view shows request history for easy replay.

Code generation exports requests as code in multiple languages. Insomnia is particularly developer-friendly for teams wanting Git-based workflows—design documents can be exported as files and committed to version control. For debugging workflows, Insomnia can capture traffic but lacks the advanced filtering, breakpoint debugging, and traffic modification that dedicated proxies offer.

It's best for developers who primarily need an API client and occasionally want to capture traffic to understand how an application communicates with APIs. The open-source core (Insomnia Core) is free forever, while Insomnia Designer and cloud features require subscription. For teams wanting lighter-weight API tooling than Postman, Insomnia provides a refreshing alternative with optional traffic capture.

Charles Proxy remains the industry standard that all these alternatives are measured against. At $50 for a lifetime license, it offers mature, battle-tested HTTP debugging with comprehensive features accumulated over 15+ years of development. Charles provides SSL proxying with certificate installation, bandwidth throttling for simulating slow connections, breakpoints for modifying live traffic, automatic/manual proxy configuration, and session recording with search and filtering.

The interface uses Java Swing, which feels dated on modern Macs but is functional and familiar to experienced users. Charles runs on Rosetta 2 on Apple Silicon Macs rather than native ARM64, making it slower than native alternatives. The extensive feature set includes Map Local for replacing remote resources with local files, Map Remote for redirecting to different servers, Rewrite rules for automatic modification, DNS Spoofing for testing different domains, and comprehensive session export options.

For teams and enterprises, Charles offers proven reliability with extensive documentation and a large community. Educational licenses are available at discounted rates. While free alternatives have caught up or exceeded Charles in specific areas, Charles remains the safe, comprehensive choice backed by years of production use across millions of developers worldwide.