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Senior Software Engineer, Firefox Security

Remote from Spain·Added yesterday (last checked 15 Oct)

Mozilla

5 open roles

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Overview

Salary: €58,000 - €77,000 a year
About €3,360 - €4,280 a month after tax, or €3,360 - €4,560 under the Beckham regime.
Work mode: Remote from Spain
English: Required
Experience: 3+ years

Visa options

The ad doesn’t mention sponsorship
Not a refusal, but not a yes. Worth asking in your first message.
Pay clears the EU Blue Card threshold
The advertised pay is over the €41,356 bar, so the route exists if Mozilla uses it.

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Skills

Nice to have

Requirements

What we're looking for

Systems programming experience and security knowledge: 3+ years of experience in low-level software engineering, strong proficiency in C and/or C++, and a solid understanding of security fundamentals.
Debugging and problem-solving skills: Experience diagnosing and resolving issues in multithreaded, cross-platform native applications, including memory and performance challenges.
Web platform and modern systems experience: Familiarity with web technologies (HTML, CSS, JavaScript) and interest or experience in Rust; ability to work effectively within large, complex, multi-language codebases.
Effective collaboration and communication: Experience working with distributed teams and communicating technical ideas clearly in writing and conversation.

Pay & benefits

What you'll get

Generous performance-based bonus plans to all eligible employees - we share in our success as one team
Generous retirement contributions with 100% immediate vesting (regardless of whether you contribute)
Quarterly all-company wellness days where everyone takes a pause together
Country specific holidays plus a day off for your birthday
One-time home office stipend
Annual professional development budget
Quarterly well-being stipend
Considerable paid parental leave
Employee referral bonus program
Other benefits (life/AD&D, disability, EAP, etc. - varies by country)

The role

What you'll do

Design, build and implement security and hardening features for enterprise users: Design, implement, test, and ship cutting-edge security features that strengthen Firefox's security posture.
Advance Firefox's security architecture across multiple operating systems: Contribute to and drive cutting-edge improvements to Firefox's core security posture, by building privilege isolation and moving trust boundaries or Strengthen Firefox's security architecture: Improve Firefox's core security mechanisms including cryptographic protocols, WebPKI, and security-sensitive web APIs.
Contribute to our security initiatives: Work across teams to investigate security issues, identify root causes, and deliver robust, maintainable fixes.
Improve browser reliability and performance: Diagnose and resolve issues affecting stability, correctness, performance, and memory usage in a complex, multithreaded environment.

Hiring Ranges

Remote Spain

€58.000-€77.000 EUR

About Mozilla

Mozilla is a global nonprofit-backed technology organization best known for the Firefox web browser, which champions an open, accessible, and private internet. The company develops a range of products including the Firefox browser, Pocket, and various privacy-focused tools, and operates through the Mozilla Foundation and its taxable subsidiary, Mozilla Corporation. With a mission-driven approach, Mozilla is a recognized leader in internet advocacy and software development, employing thousands of people worldwide.

In Spain, Mozilla has a significant engineering presence, particularly in Madrid, where teams contribute to core Firefox development and security initiatives. The company is known for its collaborative, remote-friendly culture and its commitment to open-source principles, making it an attractive employer for international engineers who value privacy, innovation, and a positive social impact. Mozilla actively hires international talent and offers a supportive environment for relocating professionals.

Founded: 1998
Employees: 1,000–5,000
Headquarters: Mountain View, USA
In Spain: Barcelona
Website: mozilla.org

Good to know if you are moving

Mozilla has a strong engineering hub in Barcelona, Spain, focusing on Firefox and security.
The company is known for its open-source culture and remote-friendly work policies.
Mozilla offers competitive benefits and supports international relocation for senior roles.
Employees often contribute to global open-source communities, providing unique networking opportunities.
The company's mission-driven focus on privacy and internet health appeals to professionals seeking meaningful work.

In their own words

About the company & team

Mozilla Corporation is the non-profit-backed technology company that has shaped the internet for the better over the last 25 years. We make pioneering brands like Firefox, the privacy-minded web browser. Now, with more than 225 million people around the world using our products each month, we're shaping the next 25 years of technology and helping to reclaim an internet built for people, not companies. Our work focuses on diverse areas including AI, social media, security and more. And we're doing this while never losing our focus on our core mission - to make the internet better for people.

The Mozilla Corporation is wholly owned by the non-profit 501(c) Mozilla Foundation. This means we aren't beholden to any shareholders - only to our mission. Along with thousands of volunteer contributors and collaborators all over the world, Mozillians design, build and distribute open-source software that enables people to enjoy the internet on their terms.

Mozilla exists to build the Internet as a public resource accessible to all because we believe that open and free is better than closed and controlled. When you work at Mozilla, you give yourself a chance to make a difference in the lives of Web users everywhere. And you give us a chance to make a difference in your life every single day. Join us to work on the Web as the platform and help create more opportunity and innovation for everyone online.

Additional information

Mozilla understands that valuing diverse creative practices and forms of knowledge are crucial to and enrich the company's core mission. We encourage applications from everyone, including members of all equity-seeking communities, such as (but certainly not limited to) women, racialized and Indigenous persons, persons with disabilities, persons of all sexual orientations, gender identities, and expressions.

We will ensure that qualified individuals with disabilities are provided reasonable accommodations to participate in the job application or interview process, to perform essential job functions, and to receive other benefits and privileges of employment, as appropriate. Please contact us at hiringaccommodation@mozilla.com to request accommodation.

We are an equal opportunity employer. We do not discriminate on the basis of race (including hairstyle and texture), religion (including religious grooming and dress practices), gender, gender identity, gender expression, color, national origin, pregnancy, ancestry, domestic partner status, disability, sexual orientation, age, genetic predisposition, medical condition, marital status, citizenship status, military or veteran status, or any other basis covered by applicable laws. Mozilla will not tolerate discrimination or harassment based on any of these characteristics or any other unlawful behavior, conduct, or purpose.

Group: D

Req ID: R3247

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