Senior user interface/web developer Work, Jobs (with Salaries)

Senior Software Engineer, WebExtensions
Mozilla —Remote
- £66,000 - £87,000 a year
- Remote
- C++
- JavaScript
- Software development
- Employee assistance programme
- Referral programme
Senior Software Engineer I (JavaScript))
RELX —London
- Full-time
- JavaScript
- APIs
- Agile
- Employee assistance programme
- Employee discount
Software engineer, generative AI (UK)
WRITER —London
- Full-time
- Hybrid work
- Azure
- AWS
- APIs
- Annual leave
Senior Software Engineer I (JavaScript))
Elsevier —London
- Full-time
- JavaScript
- APIs
- Agile
- Employee assistance programme
- Employee discount
Engineering Systems Development Specialist
Southeastern Railway —London
- £60,000 a year
- JavaScript
- Software development
- Agile
- Annual leave
Quick apply
8d
Front End Developer
Solirius Reply —London
- £40,000 - £65,000 a year
- Full-time
- Hybrid work
- Azure
- AWS
- Analysis skills
- Annual leave
- Employee assistance programme
Quick apply
Mid-Senior Wordpress Developer
StudioHub —Bridlington
- £35,000 - £40,000 a year
- Full-time
- Hybrid work
- AWS
- JavaScript
- APIs
- Work from home
Quick apply
Front End Developer (with Power Apps experience)
Amber Labs —London
- Hybrid work
- JavaScript
- Agile
- HTML
- Annual leave
- Employee discount
Quick apply
Senior Front End Software Engineer - Application Development
Palantir Technologies —London
- Full-time
- JavaScript
- APIs
- In-person
- Work from home
UX Designer - Amazon Developer, Alexa Device Applications, Devices Experience Design
Amazon Development Centre (London) Limited —London
- Full-time
- JavaScript
- Software development
- AI
Vice President, Client Platforms User Experience Designer
Ares Management —London
- Full-time
- Bachelor's degree
- JavaScript
- Financial services
Senior Flutter Engineer(EN)
Hypervolt Limited —London
- Full-time
- Hybrid work
- English
- Software development
- Work from home
Quick apply
Senior Full-Stack Developer
Applied Data Science Partners —London
- Hybrid work
- Azure
- SQL
- Analysis skills
- Annual leave
Vice President European Direct Lending Quantitative Developer
Ares Management —London
- Full-time
- CRM software
- Microsoft Excel
- Azure
Lead Front End Developer JD || Must have UK Government / PS experience
Amber Labs —London
- JavaScript
- APIs
- Agile
- Annual leave
- Employee discount
Quick apply
Senior Front End Engineer - AI Products
Citi —London
- Full-time
- Hybrid work
- Master's degree
- JavaScript
- APIs
- Annual leave
- Employee assistance programme
9d
Cloud Frontend Engineer
Signaloid —Cambridge
- £45,000 - £60,000 a year
- Full-time
- Remote
- Computer Science
- Engineering
- Master's degree
Quick apply
Tech Practice Principal - Web Tech Lead
AND Digital —Reading
- Full-time
- Hybrid work
- Azure
- Team management
- JavaScript
Quick apply
Senior Full Stack Developer - 6-month Fixed Term Contract
Singer Instruments —Minehead
- Full-time
- AWS
- Project management
- Machine learning
Sr. Front-end Engineer
Galytix —London
- English
- JavaScript
- APIs

I want to receive the latest job alerts for senior user interface/web developer

By signing in to your account, you agree to SimplyHired's Terms of Service and consent to our Cookie and Privacy Policy.

Senior Software Engineer, WebExtensions

Mozilla -
Remote

Apply Now

Job details

£66,000 - £87,000 a year

Benefits

Employee assistance programme
Referral programme

Qualifications

Rust (programming language)
CSS
C++
C
JavaScript
Software development
GitHub
APIs
Communication skills
Debugging
HTML

Full job description

Why Mozilla?

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.

About this team and role:

The WebExtensions platform powers the add-ons ecosystem in Firefox, enabling millions of users to customize their browser while keeping safety and performance at the forefront. As a WebExtensions Engineer, you will help implement new extension capabilities, improve existing APIs, and ensure that extensions remain reliable across Firefox.

As a Software Engineer on the WebExtensions team, you’ll bring a passion for exploring complex systems and creating experiences that balance developer power with user trust. You’ll work deep in the Gecko platform to evolve extension capabilities, and you’ll build UI features in Firefox that make extensions clear and manageable for users. Along the way, you’ll collaborate with experts across Mozilla and help advance cross-browser compatibility and the path toward standardization. Your work will keep extensions safe, powerful, and reliable for developers and millions of Firefox users.

What you’ll do:

Implement and maintain WebExtensions APIs and Addon Management, balancing power, safety, and performance, as well as user interfaces in Firefox.
Debug and fix issues affecting extensions in Firefox.
Collaborate with product managers, QA, and the AMO engineering team to deliver features end-to-end.
Contribute to Mozilla-owned extensions and system add-ons.
Participate in open source workflows: code reviews, pull requests, and discussions in Bugzilla/GitHub.
Support extension developers by helping diagnose issues and improving tooling/documentation.

What you’ll bring:

4+ years of professional experience in software development.
Strong proficiency in JavaScript, DOM APIs, HTML, and CSS.
Familiarity with modern browser architecture and debugging tools.
Experience with API design and integration.
Ability to navigate and learn from large codebases.
Strong communication skills and experience collaborating in distributed teams.

- Experience with Firefox internals, C++ or Rust.
- Familiarity with Android or GeckoView development.
- Knowledge of web security principles.
- Contributions to open source projects, especially in browser or extension development.

What you’ll get:

Generous performance-based bonus plans to all eligible employees - we share in our success as one team
Rich medical, dental, and vision coverage
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)

About Mozilla

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.

Commitment to diversity, equity, inclusion, and belonging

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 [email protected] 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

#LI-REMOTE

Req ID: R3020

Hiring Ranges:

Remote UK

£66,000 - £87,000 GBP

Apply Now

Refine Your Search

senior user interface/web developer jobs

Senior Software Engineer, WebExtensions

Senior Software Engineer I (JavaScript))

Software engineer, generative AI (UK)

Senior Software Engineer I (JavaScript))

Engineering Systems Development Specialist

Front End Developer

Mid-Senior Wordpress Developer

Front End Developer (with Power Apps experience)

Senior Front End Software Engineer - Application Development

UX Designer - Amazon Developer, Alexa Device Applications, Devices Experience Design

Vice President, Client Platforms User Experience Designer

Senior Flutter Engineer(EN)

Senior Full-Stack Developer

Vice President European Direct Lending Quantitative Developer

Lead Front End Developer JD || Must have UK Government / PS experience

Senior Front End Engineer - AI Products

Cloud Frontend Engineer

Tech Practice Principal - Web Tech Lead

Senior Full Stack Developer - 6-month Fixed Term Contract

Sr. Front-end Engineer

I want to receive the latest job alerts for senior user interface/web developer

Related Searches

Explore jobs in more locations

Jobseeker tools

Employer Tools

Browse

Stay Connected