DOC to DOCX — Format Comparison & Online Converter
Fast, instant DOC to DOCX conversion. No signup required. Just drop your .doc file and get .docx in seconds.
Batch Settings
Some metadata may not survive
Your DOC file may contain OLE properties metadata. DOCX has limited or no support for these metadata types. Location data (GPS), camera settings, and color profiles may be stripped during conversion.
長年親しまれてきたDOC形式も、ビジネス文書や個人的な創作物、果ては同人誌の原稿に至るまで、様々な場面で活躍してきました。しかし、現代のデジタル環境においては、より高度な機能と安定性を持つDOCX形式への移行が、作業効率と表現の幅を格段に広げます。特に、縦書きの表現力、複雑なレイアウトの保持、そして多様なフォントの埋め込みといった点で、DOCXはその真価を発揮します。古いDOCファイルをそのままにしておくのは、せっかくの表現が意図せず崩れてしまったり、共同作業者との間で互換性の問題が生じたりするリスクを伴います。大切なドキュメントを未来へと繋ぎ、より洗練された形で活用するために、この変換ツールがお手伝いします。まるで熟練の職人が古い資料を丁寧に修復するかのように、あなたのDOCファイルを最新のDOCXへと生まれ変わらせましょう。
- ビジネスの稟議書や企画書を最新環境で共有
- 漫画・小説の縦書き原稿を出版社へ送付
- 学校の課題やPTA資料を複数人で共同編集
日本においては、特に縦書き文書でのルビ（ふりがな）や圏点（傍点）の正確な表示、そして明朝体・ゴシック体といった日本語フォントの埋め込み精度がDOCX形式で格段に向上します。
About DOC to DOCX Conversion
DOC (introduced 1983) and DOCX (introduced 2006) are both document formats, but they differ in important ways. DOC is the legacy Microsoft Word format (pre-2007) — still widely circulated. DOCX is Microsoft Word's modern format based on Office Open XML — editable text documents with formatting.
Full Name: DOC uses Microsoft Word Legacy, while DOCX uses Microsoft Word Document. Compression: DOC uses None (uncompressed), while DOCX uses Lossless. Typical File Size: DOC uses 50 KB–10 MB, while DOCX uses 50 KB–10 MB.
When you convert DOC to DOCX, the goal is to upgrade to a modern format. Converting DOC to DOCX maintains high quality with CocoConvert's optimised encoder settings. Understanding these technical differences helps you choose the right format for your workflow.
Your DOC file is decoded and re-encoded as DOCX. The conversion involves 4 steps: (1) your doc file is uploaded and the format is validated, (2) the file content is decoded into its raw representation, (3) the data is re-encoded in docx format with optimal settings, (4) the converted file is ready for download.
CocoConvert's converter handles the entire pipeline server-side using FFmpeg, Sharp, and qpdf — battle-tested libraries used by streaming platforms and enterprise tools. Files are encrypted in transit and deleted within 24 hours.
This conversion is ideal when you You need maximum device and software compatibility. For the opposite direction, CocoConvert also supports DOCX to DOC conversion.
How to Convert DOC to DOCX
- 1
Upload .doc file
Select your DOC file by dragging it to the upload zone or using the file picker. Batch upload is available for multiple files.
- 2
Choose .docx
Set DOCX as the output format. The converter uses optimal settings based on the DOC→DOCX conversion profile.
- 3
Convert
The server-side engine decodes your DOC file and re-encodes it as DOCX. Processing time depends on file size and complexity.
- 4
Download result
Grab your converted .docx file. Multiple output files can be downloaded together.
What Happens When You Convert DOC to DOCX
Your DOC file is decoded and re-encoded as DOCX.
Your DOC file is uploaded and the format is validated
The file content is decoded into its raw representation
The data is re-encoded in DOCX format with optimal settings
The converted file is ready for download
DOC vs DOCX — Detailed Comparison
| Feature | .DOC | .DOCX |
|---|---|---|
| Full Name | Microsoft Word Legacy | Microsoft Word Document |
| Compression | None (uncompressed) | Lossless |
| Typical File Size | 50 KB–10 MB | 50 KB–10 MB |
| Platform Support | Universal | Universal |
| Browser Support | none | none |
| Year Created | 1983 | 2006 |
| Open Standard | No | Yes |
Should You Convert DOC to DOCX?
When to Convert
- ✓You need maximum device and software compatibility
Common Mistakes When Converting DOC to DOCX
"DOCX will be smaller than my DOC file"
DOCX uses lossless compression, so the output file is often larger than a lossy DOC. If you need a small file, DOCX may not be the right choice.
Frequently Asked Questions
What is the difference between DOC and DOCX?
DOC is the legacy Microsoft Word format (pre-2007) — still widely circulated. DOCX is Microsoft Word's modern format based on Office Open XML — editable text documents with formatting. Full Name: DOC uses Microsoft Word Legacy, while DOCX uses Microsoft Word Document. Compression: DOC uses None (uncompressed), while DOCX uses Lossless. Typical File Size: DOC uses 50 KB–10 MB, while DOCX uses 50 KB–10 MB.
Does DOC to DOCX conversion affect quality?
Converting DOC to DOCX maintains high quality with CocoConvert's optimised encoder settings.
Which format has better compression, DOC or DOCX?
DOC uses none compression. DOCX uses lossless compression. The better choice depends on whether you prioritize file size or quality.
How long does DOC to DOCX conversion take?
Most conversions finish in seconds. Larger files or complex document content may take 10–30 seconds. CocoConvert processes files in parallel for batch jobs.
Is DOC or DOCX better for long-term storage?
DOCX is better for archival since it preserves all original data.
Versions are pinned in our worker Dockerfile and re-built via CI on every change.