JSON
Dev handoff, CI pipelines, programmatic processing
Sidenote is online proofing software built for HTML documents — the format the web actually uses. Annotate elements, track versions, export structured feedback, and let AI agents close the loop.
Reviewers never need an account · Free plan included
Traditional online proofing tools were designed for PDFs and static images — formats with fixed coordinates where a pin drop makes sense. But the web is fluid. Elements reflow, viewports resize, and content updates constantly. Dropping a pin on a screenshot of a responsive page doesn't tell your developer anything useful. Sidenote proofs the actual HTML document, anchoring annotations to DOM elements that survive layout changes, version updates, and responsive breakpoints.
| Feature | Traditional proofing | Sidenote |
|---|---|---|
| Annotation target | Pixel coordinates on a screenshot | DOM elements in live HTML |
| Layout changes | Annotations break or misalign | Annotations re-anchor automatically |
| Version comparison | Overlay two static images | Structural HTML diff with element tracking |
| Accessibility checks | Separate tool, separate workflow | WCAG 2.1 AA scan inline, every version |
| AI agent integration | None — feedback locked in proprietary UI | MCP protocol — agents read, write, iterate |
| Reviewer accounts | Required for most tools | Never required — name entry only |
Drop in your HTML file, PDF, or image. Sidenote renders it exactly as your audience would see it — because for HTML, it is rendering the actual page.
Send the link to anyone — clients, stakeholders, teammates. They enter their name and start clicking elements to leave feedback. No signup. No password. No invite email.
Every annotation is anchored to a specific element in the page. Export as JSON for your dev team, generate a PDF summary for clients, or let an AI agent read it via MCP and iterate automatically.
Most proofing tools place annotations at pixel coordinates on a flat image. Resize the window, update the layout, or switch to mobile — and every annotation is in the wrong place. Sidenote anchors annotations to actual DOM elements using a text-offset anchoring system. Click a heading, a paragraph, an image, a button — the annotation attaches to that element and stays attached even when the page changes.
Tag each annotation as a bug, suggestion, question, or praise. Reply in threads to discuss specifics. Suggest replacement text directly on the element. Resolve annotations when they're addressed — they collapse but stay in the history for traceability.
Upload a revised document and Sidenote shows you a structural visual diff — not a pixel overlay of two screenshots, but an actual comparison of what changed in the HTML. Elements added, removed, or modified are highlighted. Previous annotations re-anchor to matching elements automatically using fuzzy text matching.
Side-by-side version comparison lets reviewers see both versions simultaneously. Threaded conversations carry forward across versions, so you can trace how each piece of feedback was addressed. No more starting over every time the design changes.
Every document gets an automated WCAG 2.1 AA scan inline — contrast ratios, missing alt text, heading hierarchy, form labels, ARIA attributes. Findings appear alongside human annotations so your team sees accessibility issues in the same workflow as design feedback.
Click any finding to jump to the exact element. Upload a new version and the scan runs again automatically, so you can verify fixes without switching tools. No other online proofing tool includes accessibility auditing — it usually lives in a separate audit tool that nobody checks until after launch.
More content starts with AI now — landing pages, reports, email templates, documentation. The first draft appears in seconds. The review still takes days because it happens in screenshots and email threads that AI can't read.
Sidenote supports the Model Context Protocol (MCP) with OAuth 2.1 authentication. AI agents from Claude, ChatGPT, and other MCP-compatible tools can upload documents, read your team's annotations as structured data, and push revised versions — creating a closed feedback loop without manual copy-pasting.
Sidenote doesn't compete with your AI. It gives your AI agent a seat at the proofing table.
Every review session exports in the format your workflow needs. Pro plans include API access for automated export pipelines.
Reviewers, clients, and stakeholders comment free on every plan — no per-seat tax on collaboration.
FAQ
An online proofing tool lets teams review, annotate, and approve digital content in a shared workspace — replacing email threads, screenshot markup, and scattered feedback. Sidenote is an online proofing tool built specifically for HTML documents, so annotations anchor to actual page elements instead of pixel coordinates on a static image.
PageProof proofs PDFs and images using coordinate-based annotations. Sidenote proofs HTML documents with annotations that anchor to DOM elements — they survive layout changes and responsive breakpoints. Sidenote also includes built-in WCAG 2.1 AA accessibility auditing, MCP integration for AI agents, and requires no account for reviewers.
Sidenote supports HTML documents, images (PNG, JPG, SVG, GIF), and PDFs. HTML is where it's strongest — annotations anchor to actual DOM elements, version diffs are structural, and accessibility auditing works inline. PDF and image proofing use coordinate-based annotations.
No. Send a review link and reviewers enter their name to start commenting. No passwords, no invites, no account creation. This removes the biggest barrier to collecting feedback — stakeholder friction.
Sidenote runs a WCAG 2.1 AA automated scan on every document. It checks contrast ratios, missing alt text, heading hierarchy, form labels, ARIA attributes, and link text. Findings appear inline — click one to jump to the exact element.
Sidenote supports the Model Context Protocol (MCP) with OAuth 2.1 authentication. AI agents from Claude, ChatGPT, and other MCP-compatible tools can upload documents, read annotations as structured data, and push revised versions — creating a closed feedback loop between human reviewers and AI.
JSON exports include the annotation text, author, timestamp, element selector, surrounding text context, annotation type (bug, suggestion, question, praise), resolution status, and thread replies. PDF exports include a visual summary with screenshots. Markdown exports are formatted for handoff.
Not yet. Sidenote is in early access. Documents are private by default, data is encrypted in transit and at rest, and we don't train on your content. SOC 2 certification is planned as the platform matures.
Free: 5 documents, 3 versions each, unlimited reviewers, WCAG auditing. Pro: $19/month — unlimited documents, MCP access, brand auditing, JSON export, API access. Team: $22/seat/month — shared workspaces, role-based permissions, team analytics. Reviewers are always free on every plan.
Yes. Share a review link with your client — they enter their name and start leaving feedback. Pro plans support password-protected links and expiring share links for added control over who sees what and when access revokes.