Hongbi

Mark up, measure and edit drawings in the browser

Mark up a PDF and measure it,
without uploading anything.

Hongbi is a markup tool that runs the moment you open the page. Draw boxes, write notes, set a drawing scale and measure real dimensions — then export a PDF or an image with a numbered comment list attached.

Everything happens inside your browser. There is no server that could hold your files — this isn't a promise not to look, it's that the file technically never leaves the device. It works with the network off.

Open Hongbi

No install, no signup, free. Works with PDF, JPG and PNG.

Measuring on construction drawings

This is the biggest difference from a general PDF tool. Set the drawing scale (1:100, 1:150, whatever it is) and you can measure distances directly on the sheet — the numbers come back as real centimetres or metres, not screen pixels.

Scale — type 1:N directly, or calibrate by measuring a known length
Dimensions — three points, and it labels the actual size
Angles — three points, and it reports the included angle
Snapping to the drawing — while measuring you can snap to corners, endpoints, midpoints and intersections inside the PDF itself

Why architects and contractors need this

A client sends a PDF floor plan and asks how thick that wall is, or how wide the opening is. A normal PDF reader can't tell you the real size, and opening AutoCAD means having both the source file and a licence. Hongbi just needs the scale — and it works on a phone.

PDF to DXF

Pull the vector linework out of a PDF and write it to DXF so CAD can open it. You can also explode just one region — draw a box, and the lines inside become editable polylines you can move, trim and delete, then merge back into the sheet.

Markup tools

Boxes, ovals, polylines, curves Revision clouds Arrows, lines, arcs, shapes Freehand and highlighter Text (vertical CJK, tracking, leading) Numbered comments Stamps and signatures Flood fill for closed areas

The exported PDF contains real PDF annotations — the recipient can click and reply to them in Acrobat. They are not flattened into a picture.

CAD commands

Beyond markup there is a set of CAD-style editing commands. You can type the shortcut straight into the command line:

Command	What it does
M · Move	Move the selection somewhere else
CO · Copy	Place a copy at a point you pick
MI · Mirror	Mirror across an axis
RO · Rotate	Rotate about a point
SC · Scale	Scale uniformly
TR · Trim	Cut the segment between two intersections
EX · Extend	Extend to the nearest boundary
O · Offset	Parallel copy at a distance you give
AR · Array	One item becomes a row
FI · Fillet	Round the corner between two lines

PDF utilities

18 everyday PDF tools, all running in the browser:

Merge PDFs (reorderable) Split into single pages PDF to images / JPG Images to PDF Compress (choose quality) Page numbers and watermarks Rotate all, reverse page order Organise pages (drag, delete) Photo to scanned document Remove white background, shrink photos Extract embedded images Strip AutoCAD's hidden annotations

Redaction actually removes the text

In most tools "redact" just paints a black rectangle on top — the text is still in the file, and copy-paste brings it back. Hongbi re-renders those pages, so the text objects no longer exist.

Questions

Do I need an account? Is it paid?

Neither. Open the URL and use it. No account, no trial period, no watermark.

Are my files uploaded?

No. There is no server that processes files — all of it runs in your browser. Open the network tab in developer tools and watch, or simply turn the network off and keep working.

Does it work on a phone?

Yes. The interface is laid out for phones, and you can "Add to Home Screen" to use it like an app. Drawing with an Apple Pencil records pressure.

Does it work offline?

Yes. After the first visit it's cached — you can open it, mark up and export with no connection at all.

Where are my files stored?

In this device's browser storage (IndexedDB). They don't sync to other devices — that's deliberate, because syncing would require a server.

What formats are supported?

Reads PDF, JPG and PNG. Exports PDF (with real annotations), JPG, PNG and DXF.

Is it available in English?

Yes. The interface follows your browser language, and you can switch it manually under Settings. The tool was originally written in Traditional Chinese.

Who made this

I'm a designer working at an architecture practice in Taiwan. I wrote Hongbi because I mark up and measure construction drawings every day, and the available tools either wanted my files uploaded or couldn't give me a real dimension.

Open source components used: pdf.js (Apache-2.0), pdf-lib (MIT), jsPDF (MIT), KDBush (ISC).