Senior Software Engineer - JavaScript (Client Side)

As a Senior JavaScript Engineer, you will be required to work on various JavaScript libraries that are served on our customers’ websites thereby impacting millions of users. These libraries are the core of all the features of VWO.

We love vanilla JavaScript and work with cutting-edge technologies like TypeScript, Rollup.js, Cypress, ESLint.

We are obsessed with Web Performance. See some of the improvements that we did https://engineering.wingify.com/posts/performance-improvements-in-vwo-smart-code/

Job Responsibilities:

• Development of Core JavaScript libraries.
• Writing reusable code or modules that can be used across all the JavaScript libraries.
• Talking about your work - we love open source software, we heavily use them, and talking about how we use them is the least we can do to help the community. See our engineering blog and our GitHub page

Skills & Experience:-

• 4- 6 Years of Experience in Software Development
• Passion for writing Vanilla JavaScript
• Strong knowledge and experience in JavaScript, HTML, CSS.
• Work Experience with TypeScript
• Deep understanding of the DOM, Browser Events, JavaScript APIs, Canvas rendering, etc.
• Deep understanding of how the browsers work.
• Regard for optimizations that focus to deliver content to the user as quickly as possible.
• Awesome Debugging Skills.
• Passion to write automated tests to verify the working of libraries (You can’t possibly verify things on all devices and on all browsers manually). We use Cypress for this.
• Understanding the similarities and differences across browsers (young and old).
• Experience in writing modular JavaScript code
• Knowledge of high-level programming concepts like promises, data-binding.
• Passion to stay up to date with the constantly evolving world of front-end development.

About VWO

VWO is a leading Digital Experience Optimization platform trusted by over 3,000 businesses in 100+ countries, including global brands like Samsung, Vodafone, Toyota, HBO, and Domino's. What began 15 years ago as one of the world’s first A/B testing tools has since evolved into a comprehensive, enterprise-grade platform used by product, marketing, and growth teams to experiment, personalize, analyze behavior, and build exceptional digital experiences.

Today, VWO offers a full-stack suite for A/B testing, multivariate testing, feature rollouts, heatmaps, session recordings, behavioural analytics, surveys, personalization, and more across web, mobile, and server-side applications — all in one unified platform. We enable teams to make confident, data-driven decisions that drive user engagement, retention, and conversion.

VWO is a profitable, founder-led business with $50M+ ARR, strong EBITDA margins, and a history of capital-efficient, sustainable growth. In January 2025, Everstone Capital acquired a majority stake in the company to help accelerate our global expansion — both organically and inorganically.

We are a fully remote team of 450+ people, with go-to-market teams across the Americas, Europe, and APAC, and product and engineering anchored in India. Our culture values deep thinking, fast execution, and strong ownership — with minimal bureaucracy and high autonomy. Despite our scale, we continue to operate with the agility and ambition of a startup.