Senior Frontend Engineer, Marketing Website

AI Startups UK; Greater London; On-site; GBP 90,000 - 120,000; Full time

Job summary

Synthesia, the world’s leading AI video platform, is seeking a Senior Frontend Engineer for the Website team to own the component library, content model and rendering stack that powers synthesia.io. You’ll shape direction and make key technical decisions with broad context across the system, delivering high-quality component and schema code and supporting tooling.

Millions visit synthesia.io monthly; you’ll ensure accessibility, performance and SEO at scale while handling localisation across

Qualifications

• At least five (5) years as a software engineer, including three (3) at senior level, building front end for content-driven or marketing platforms.
• Real ownership of a content model in Sanity; experience with GROQ and Portable Text.
• Deep front-end expertise: HTML, CSS and TypeScript, with strong component API design.

Responsibilities

• Build, scale and evolve the section library: Astro components, Sanity schemas and design tokens.
• Own the content model; design schemas that resist misuse and enable editors or agents to build correctly by construction.
• Take Figma specs to production: responsive, accessible by default, and aligned with design intent.
• Extend the platform for AI-assisted development, enabling AI agents to generate on-brand sections from a design spec.
• Own SEO integrity: canonicals, sitemaps, structured data, redirects, and avoid traffic cliffs on launch.
• Raise engineering standards across the site with thorough code review, patterns and tests.
• Maintain localisation across nine locales and a translation pipeline for a global audience.

Skills

Front-end development

HTML/CSS/TypeScript

Sanity content model

SEO & performance

Communications

Job description

Synthesia is the world’s leading AI video platform for business, used by over 90% of the Fortune 100. Founded in 2017, the company is headquartered in London, with offices and teams across Europe and the US.

As AI continues to shape the way we live and work, Synthesia develops products to enhance visual communication and enterprise skill development, helping people work better and stay at the center of successful organizations.

Following our recent Series E funding round, where we raised $200 million, our valuation stands at $4 billion. Our total funding exceeds $530 million from premier investors including Accel, NVentures (Nvidia's VC arm), Kleiner Perkins, GV, and Evantic Capital, alongside the founders and operators of Stripe, Datadog, Miro, and Webflow.

About the role

As a Senior Frontend Engineer on our Website team, you'll be a co-owner of the platform behind synthesia.io: the component library, content model and rendering stack that every page on our marketing site is built from. You'll shape direction and make key technical decisions with the team, likely with a focus area of your own but context across the whole system. This is a hands‑on engineering role, and your primary output is high‑quality component and schema code, plus the tooling that lets others build with it.

Millions of people visit synthesia.io every month, and it is one of the main ways we win new customers. That comes with real responsibility. The decisions you make are seen at scale, and we set the quality bar accordingly.

The defining challenge of this role is composability: a marketing site that marketers, and increasingly AI agents, can build pages with, without breaking design, performance or SEO.

You can expect to:

• Build, scale and evolve our section library: the Astro components, Sanity schemas and design tokens that let us compose marketing pages consistently and accessibly.

• Own the content model. Design schemas that resist misuse, so an editor, or an agent, can build a page that is correct by construction rather than correct by review.

• Take Figma component specs all the way to production: responsive across mobile, tablet and desktop, accessible by default, matching design intent precisely.

• Extend the platform for AI‑assisted development, so coding agents can generate on‑brand, on‑spec sections from a design spec as reliably as a person can.

• Own SEO integrity as a first‑class engineering concern: canonicals, sitemaps, structured data, redirects, and no traffic cliffs on launch.

• Raise the bar on engineering standards across the website surface: thorough code review, patterns others can follow, and tests around the parts that actually break.

• Maintain and extend localisation across nine locales and a translation pipeline, so the system works for a global audience.

• Shape the technical direction of the website platform over the next 6 to 12 months, and champion its adoption with the people who publish on it.

What we're looking for

• At least five (5) years as a software engineer, including three (3) at senior level, building front end for content‑driven or marketing platforms.

• Real ownership of a content model in Sanity. You've designed schemas other people had to live with, and you have opinions about references vs. embedded objects, when a variant belongs in the schema versus at runtime, and how to stop a section library sprawling. GROQ and Portable Text are familiar territory.

• Deep front‑end expertise: expert HTML, CSS and TypeScript, with a strong command of component API design and the developer experience of a shared library.

• You can work end to end. Comfortable owning the server side as well as the front end: SSR, serverless and edge runtimes, API routes, a SQL database, secrets and CI. You should be able to take a feature from schema to component to the route that serves it without handing off, and be happy debugging something that only reproduces in production.

• Solid understanding of responsive design, cross-browser compatibility and web performance, and comfortable building to WCAG 2.2 AA. Accessibility is part of your definition of done, not a separate pass.

• You care that marketing sites are measured, on performance, SEO, analytics events and conversion, and you're happy being accountable to those numbers.

• A strong sense of craft and attention to detail, and the judgement to balance design intent against engineering constraints.

• Strong communication and collaboration skills. You explain your reasoning, review generously, and treat levelling up the people around you as part of the job.

Nice to haves

• Prior experience working on a large SaaS marketing website, at real traffic and with real stakes attached.

• Astro, or another islands or static‑site framework.

• Cloudflare Workers, or another edge or serverless platform.

• Experience with AWS Lambda.

• Tailwind CSS v4, and experience working from a token‑based design system.

• Experience, or strong interest, in making component libraries and content models consumable by AI agents.

• A strong design sensibility: an eye for visual detail and the judgement to push back on and improve design decisions, not just build them.

• Experience with localisation and internationalisation at scale for a global audience.

• Analytics and tag management implementation: dataLayer events, server‑side tagging, getting attribution right without hurting performance.

Our culture

At Synthesia we're passionate about building, not talking, planning or politicising. We strive to hire the smartest, kindest and most unrelenting people and let them do their best work without distractions. Our work principles serve as our charter for how we make decisions, give feedback and structure our work to empower everyone to go as fast as possible. You can find out more about these principles here.

The hiring process:

• 30 min call with our Technical Recruiter

• 45 min call with the Head of Website about your past projects

• 75 min practical exercise with one of our engineers. We hand you a real Figma section spec and work through how you'd model and build it. Collaborative, not Leetcode.

• 60 min call with leadership, focused on examples of collaboration, growth, and the details of your future team.

Other important info:

• Our preference is for this role to be based either in‑office or remote in London, UK. We can also accommodate remote workers elsewhere in Europe subject to compliance and right to work checks.

• This is full‑time employment only, usually through OysterHR. No contractors possible.