HWP & HWPX explained

1. What is HWP?

HWP is the native document format of Hancom Hangul (한글), the word processor dominant in Korean government, schools, courts and many enterprises. Legacy .hwp is a binary format owned by Hancom. Since 2010 the newer HWPX has been published as national standard KS X 6101 — a ZIP archive of XML files similar in philosophy to .docx.

2. Why layout breaks during conversion

• Legacy HWP binary is only fully specified inside Hancom Office. Open-source renderers (hwp5, LibreOffice) reverse-engineered it, so table cell alignment, footnote anchors and some shapes do drift.
• Korean fonts (Batang, Gulim, Malgun Gothic, HY signatures) are often referenced but not embedded. If your converter machine lacks the font, characters show as tofu (□) or get substituted with a different metric, shifting line wraps.
• Page layout features — drop caps, custom tabs, footnote separators, mixed-column tables — were Hancom-extensions not cleanly mapped to PDF.

3. Which format to prefer

If you author new documents today, save as HWPX. It is a government-published open standard, so third-party tools (including LibreOffice) support it more faithfully than the old binary form. For archived legacy files, conversion via Hancom’s own viewer is the safest path.

4. Fidelity ranking by method

1. Hancom Office Viewer + Print to PDF (Windows, free) — uses Hancom’s own engine, near-perfect.
2. Naver Office → Save as PDF — Naver licenses Hancom render pipeline; very close to #1 with occasional shape drift.
3. LibreOffice --convert-to pdf — great for hwpx, acceptable for simple hwp, but tables / footnotes can shift.
4. Generic online converters — last resort. Font and layout quality is a lottery.

5. Privacy and PII

Korean government HWP documents often embed personal data (resident registration number, addresses). Avoid uploading them to third-party online converters. Prefer the local LibreOffice path or run Hancom Viewer on an offline workstation.

6. Bulk conversion pattern

# requires libreoffice installed
mkdir -p pdf
for f in *.hwp *.hwpx; do
  [ -e "$f" ] || continue
  soffice --headless --convert-to pdf --outdir pdf "$f"
done

This pattern works on macOS, Linux and WSL. Install Korean system fonts (fonts-noto-cjk on Ubuntu, Noto Sans CJK KR bundle on macOS) before running on a fresh machine to prevent tofu characters.

7. Round-tripping HWP ↔ DOCX ↔ PDF

Going HWP → DOCX → PDF (e.g. via LibreOffice) double-compounds layout drift. If PDF is the real target, convert straight to PDF in one step — fewer intermediate re-layouts, better fidelity.