Altium SchDoc Viewer

Altium Designer is one of the most used tools for designing circuit boards, and its schematic sheets are saved as .SchDoc files. A licence costs thousands of dollars a year and the program only runs on Windows, so when a contractor, a supplier, an open hardware project or a colleague sends a .SchDoc, the person receiving it often cannot open it. Altium's own online viewer asks you to upload the design to the cloud, which many companies do not allow for unreleased products, and free desktop alternatives need installing and often cannot read the format at all.

This page reads the file itself. A binary .SchDoc is a Microsoft compound file, the container older Office files use, holding a list of records: the sheet, each part with its pins and graphics, wires, buses, net labels, power symbols, ports, sheet symbols, notes and pictures. SchDocOpen unpacks the container in your browser, reads every record and redraws the sheet as a vector picture in the colours saved in the file, with the border, zones and title block. ASCII .SchDoc files, including those exported by EasyEDA, work too. Multi-part chips show the right part (U1A, U1B), hidden pins and parameters stay hidden, and pictures stored inside the file are placed on the sheet.

A schematic is more than a drawing, so the page also works out connectivity the way Altium does by default. Wires join at their ends, at junction dots and where one wire ends on another; pins, net labels, power symbols, ports and sheet entries join the wire they touch, and nets with the same name join across sheets. Tap a part for its pin by pin net list, tap a wire to see every pin on that net, or download the netlist and a bill of materials grouped by value and footprint. That answers the questions people usually have when someone sends a schematic: what is this part, what is it connected to, and what do I need to buy.

Speed matters, because a viewer you wait for is a viewer you close. The reader is about 20 KB compressed and loads in the background while this page is idle. It runs in a worker, so the page never freezes, and it draws the first sheet before the rest. A typical sheet shows in well under a second, and a project of dozens of sheets shows progress as each one is drawn.

Your design stays on your device. The file is read by code running in this tab, and the PDF, PNG, SVG and CSV files are made on your computer too. Nothing is uploaded, there is no account, and the file is gone when you close the page, which matters for circuits that are under NDA or not yet released.

Some things are drawn more simply than in Altium: fonts missing from your device are swapped for a close match, pictures linked from another file show as a grey box, and the net list follows Altium's automatic net scope rather than a custom project setting. PCB layouts (.PcbDoc), schematic libraries (.SchLib) and Protel 99 SE files are not opened here. Altium and Altium Designer are trademarks of Altium Limited; TaskNinja is not affiliated with Altium.