Freelance Developer – Fintech

Join a project focused on developing a Chrome extension that streamlines the process for users to download their KSeF certificate from a government portal and upload it securely to a fintech SaaS platform. This role is ideal for an experienced developer with a strong background in browser extension development, particularly for Chrome, and an understanding of secure file handling and REST API integration. The extension will guide users through a step-by-step process, ensure compliance with Chrome Web Store requirements, and provide clear user feedback throughout. You will play a key role in both the technical build and the successful publication of the extension.

Deliverables

• Develop a fully functional Chrome extension using Manifest v3, JavaScript or TypeScript, and Chrome APIs.
• Implement a guided workflow for users to download and upload KSeF certificates.
• Integrate secure file detection, handling, and REST API communication for uploads.
• Conduct validation checks and ensure GDPR compliance.
• Provide user and technical handover documentation.
• Assist with the Chrome Web Store submission process and address any compliance feedback.
• Deliver clean, well-documented source code.
  
  

Requirements

• Proven experience building and publishing Chrome extensions, including Manifest v3.
• Proficiency in JavaScript or TypeScript and Chrome extension APIs.
• Strong understanding of secure file handling and authentication flows.
• Experience with REST API integration.
• Familiarity with GDPR and Chrome Web Store compliance.
• Ability to create clear user and technical documentation.
• Experience with fintech, ERP, or e-invoicing systems (especially Polish KSeF) is a plus.
• Available to start within 1–2 weeks and deliver within 2–4 weeks.
• Excellent communication skills and attention to detail.
  
  

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