Specpin pins business specifications (rules, descriptions, acceptance criteria) directly onto the elements of a running web interface, then displays them right in the browser when you hover or browse the page.

Specpin is NOT a code generation tool from specifications: it does not produce any application code. This is a knowledge layer that pins always-updated documentation, version-managed with Git, onto the interface you currently have. Specifications are in JSON format in the .specs/ directory of the repo and are served to the utility by a small local Go sidecar via localhost with token authentication. By default, nothing leaves your machine.

Features:

- Pin specifications to real elements on the page: robust multi-signal fingerprinting (test-id, aria, selector, xpath, text, location) to keep specifications matched after refactoring, limited to pages by URL glob.

- Matching reliability and page status: see how each specification matches (exact anchor or selector), review fragile matches, and add data-spec-id attributes for precise matching.

- Three display modes: tooltip, side panel, and draggable modal. Switch by a click or Alt+Shift+M.

- Manual capture: click on an element and draft specifications right on the spot, no need to leave the page. Toggle capture mode with Alt+Shift+C.

- Local projects can be written: edit, capture, create, delete, and export specifications in zip format, even without a running sidecar.

- Connect multiple projects: one utility serving multiple projects simultaneously, routing to each page by origin, with individual toggle for each project and source label (sidecar or local).

- Guide mode: onboarding tour based on specifications with two scopes (group, commit to repo; individual, by origin), including spotlight overlay and anchored popover.

- Side panel interface: open Specpin in the side panel of Chrome with inline specification details and live auto-refresh.

- Specification search: client-side filtering by title, file, tag, and description.

- Multilingual specification content: strings by locale with a language switch in the browser and tab editing for each locale.

- Markdown formatted specifications: descriptions and business rules support a safe subset of Markdown (bold, italic, inline code, links, lists), authored through the toolbar and displayed across all surfaces.

- User-selected themes: System / Light / Dark, with design tokens for both themes.

- Three-language interface (EN + VI + JA), independent of the specification content language.

Security by default: the default sidecar listens on 127.0.0.1 (remote is optional via your own HTTPS reverse proxy), using bearer-token authentication, only accepting CORS from the utility's origin, and preventing path traversal when writing. Open source, built with Manifest V3. No data collection, no tracking, no remote code execution.