WinHelp

A browser-based viewer for Windows .hlp files, the legacy WinHelp format used across Windows 3.x, 95, 98, NT and early 2000s applications. Parsing is done in C compiled to WebAssembly; rendering is plain HTML/CSS/JS.

Open a file via the file picker or drag-and-drop. Files are cached locally in IndexedDB and can be re-opened from the cached-files dropdown. No data ever leaves the browser.

Features

File format

• Windows 3.x (HC30, HC31) and Windows 95+ (HCW 4.x) help files
• LZ77 and RLE decompression
• v3.0 (|Phrases) and v4.0 (|PhrIndex + |PhrImage) phrase compression
• Internal directory B+ tree traversal
• |TOPIC streaming with random-access block map

Rendering

• Paragraphs with indents, alignment, borders, tab stops, line spacing
• Font table with size, weight, italic, underline, strikeout, small caps, colors
• Jump links, popup links, macro links (green with WinHelp underline style)
• Tables (cell widths, borders, alignment)
• Non-scrolling and scrolling regions
• Embedded bitmaps (DIB / device-independent) and segmented hypergraphics (SHG) with clickable hotspot overlays
• Windows metafiles (WMF)
• Windows codepages (1250-1258), plus Shift_JIS, EUC-KR, GB2312, Big5 via charset detection or LCID fallback
• Right-to-left layout for Arabic and Hebrew files
• Bundled open-source replacement fonts (MS Sans Serif, Tahoma, Courier, Fixedsys, Symbol, Wingdings, Marlett)

Navigation

• Topic hyperlinks, keyword index search, context / JumpID lookups
• Browse Prev/Next sequences
• Contents, Top, Print, Back toolbar buttons
• URL hash deep-linking (#file/topic-N and #file/index/<query>)
• File cache to reload without re-upload

Macros

• JumpHash, JumpContext, JumpID, JumpContents
• PopupHash, PopupContext, PopupId
• ALink, KLink (with context/hash fallback)
• CreateButton, DisableButton, EnableButton, DestroyButton, ChangeButtonBinding
• BrowseButtons, Back, Prev, Next, Contents
• ExecFile / EF (opens http://, https://, mailto: targets)
• Print, and common aliases (JH, JC, JI, PC, PI, AL, KL, CB, DB, EB, CBB)
• Chained macros separated by ;
• Startup macros from |SYSTEM

Not supported

• EMF (Enhanced Metafile) rendering — only WMF; EMF embeds inside WMFs are not decoded
• Full-text search (|FTINDEX)
• Multimedia Viewer extensions beyond basic MVB font compatibility
• Cross-file links to external .hlp files
• DLL-registered macros
• Annotation (.ANN) files
• Contents (.CNT) files

Build

Requires make. The Zig toolchain is downloaded automatically on first build.

make          # builds dist/hlp.wasm
make fonts    # converts fonts/*.ttf to fonts/woff2/*.woff2 (depends on woff2_compress)
make serve    # build + static server + auto-rebuild watcher (depends on fswatch)

License

See LICENSE for attribution of referenced projects (Wine, helpdeco, Manfred Winterhoff's format documentation) and vendored dependencies (TLSF, stb, Wine fonts).