Senior Software Engineer - Browser

About the role

We're looking for a Senior Software Engineer to join our Stealth & Reverse Engineering team-the elite force responsible for making our headless browsers and traffic completely undetectable by modern anti-bot systems. You will own and evolve our custom fork of Chromium, continuously identifying and patching all behavioral and fingerprinting vectors that reveal automation. You'll go deep into browser internals, reverse engineer anti-bot defenses, and create a fully cloaked browsing experience across real-world targets. You'll also build internal tools that detect, analyze, and resolve JavaScript-based bot challenges (like fingerprinting, integrity checks, proof-of-work, and obfuscation traps), and help automate evasions across our infrastructure. This is a deeply technical, adversarial, and high-leverage role at the heart of what makes our scraping infrastructure world-class. We're a remote-first company with a fast-paced, high-impact culture. In this role, you'll work closely with our CEO, Aurken, and our Director of Engineering. And as a business with two technical founders who have strong engineering backgrounds-you must be comfortable engaging in technical discussions while balancing business needs.

Responsibilities

• 🧬 Browser Fingerprinting & Chromium Patching
• Own and evolve our Chromium fork, maintaining full control over browser behavior and instrumentation.
• Patch and neutralize browser fingerprinting surfaces: canvas, audio, WebGL, screen, navigator, user agent, and more.
• Harden the browser against integrity checks (function.toString, error stack traces, memory layout, etc.).
• Ensure parity with real users under advanced detection tools like FingerprintJS, Datadome, PerimeterX, and others.
• 🔬 Reverse Engineering & Challenge Automation
• Analyze real-world JavaScript challenges and traps designed to detect bots.
• Reverse engineer obfuscated payloads and evasive scripts using tools like Chrome DevTools, Frida, Wireshark, mitmproxy, etc.
• Build internal tooling to automatically detect, triage, and solve bot challenges, integrating into our scraping runtime.
• Develop detection signatures for new anti-bot mechanisms and continuously track vendor evolution.
• 🧰 Internal Tooling & Automation
• Build robust internal libraries to spoof browser behavior, intercept and manipulate DOM/state, and bypass anti-bot logic.
• Create automated pipelines that detect detection, trigger browser patches, or escalate to manual review.
• Integrate JavaScript instrumentation and DOM mutation trackers to flag stealth issues before customers do.
• 📊 Observability, Resilience & Safety
• Build internal dashboards to monitor fingerprint mismatches, challenge rates, JS errors, and detection spikes.
• Proactively identify and mitigate stealth regressions caused by Chromium updates or vendor changes.
• Help maintain and evolve our internal stealth testbed, simulating dozens of anti-bot vendor environments.
• 🧠 Technical Leadership & Deep Expertise
• Be the team's go-to expert in browser internals, bot detection evasion, and security-focused reverse engineering.
• Mentor engineers in topics like V8 internals, JS fingerprinting, and browser automation stealth.
• Help define our long-term strategy around browser-level evasion and undetectable scraping at scale.
• The Person:
• You're the kind of engineer who doesn't just use tools-you tear them apart to understand exactly how they work. You're fluent in browser internals, and you treat anti-bot systems as adversaries to outsmart.
• You're comfortable working in the gray areas of web security, JavaScript instrumentation, and reverse engineering. You love automation, can write clean low-level code, and know how to survive in hostile runtime environments.
• This role is for a rare breed of engineer who's part hacker, part builder, and 100% obsessed with invisibility.
• Key Skills and Experience:
• 5+ years of software engineering with a focus on browsers, reverse engineering, or automation in adversarial environments.
• Fluency in C++ and JavaScript (Node or browser), with ability to write clean, testable low-level c

Benefits

Additional Information

Senior Software Engineer (EMEA) Born out of the heart of the Basque Country in Bilbao, ZenRows is one of the fastest-growing startups in Europe! We work 100% remotely and believe in hiring the best people, no matter where you are in the world! Founded in 2021, our mission is to transform the future of data workflows by enabling seamless, large-scale data extraction from the web. With our powerful tools, businesses can automate data collection at scale while leveraging the most advanced anti-bot bypass system on the market. Thousands of companies worldwide-across industries like e-commerce, real estate, finance, and AI-rely on ZenRows to streamline their data pipelines, fueling automation, analytics, and AI-driven insights As we continue our rapid expansion, we are now looking for a Senior Software Engineer to join us on a permanent basis and make an instant impact.

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