DOC to DOCX Converter

What is DOC to DOCX Conversion?

DOC to DOCX conversion transforms a document from the outdated Microsoft Word 97-2003 binary format to the modern Office Open XML format used in Word 2007 and all subsequent versions. During conversion, all document content is preserved: text, tables, images, styles, and formatting.

The DOC format was created by Microsoft in 1983 and was used for over twenty years as the primary text document format. It is a closed binary format with an undocumented structure that was poorly supported by third-party programs. DOC files store data in a specific binary form, making them vulnerable to corruption and difficult to process.

In 2007, with the release of Microsoft Office 2007, the company introduced the new DOCX format based on the open Office Open XML (OOXML) standard. A DOCX file is technically a ZIP archive containing structured XML files with text, formatting, styles, and media content. In 2008, OOXML was approved as the international standard ISO/IEC 29500, establishing DOCX as a universal document format.

PEREFILE service performs DOC to DOCX conversion with maximum preservation of the source document's structure and formatting. Conversion is fast and requires no software installation on your computer.

Why DOC is Considered an Outdated Format

The DOC format served for over two decades, but technology has changed, and today this format has significant disadvantages:

Technical Obsolescence

The binary structure of DOC was created in an era when computers were significantly less powerful. Developers optimized the format for the limited resources of that time, sacrificing flexibility and compatibility. Today, these compromises create problems:

• Closed specification — until 2008, the DOC format was completely closed, making it difficult to create compatible programs
• Vulnerability to corruption — the binary structure is sensitive to bit errors, and a damaged file is difficult to recover
• Limited size — the format has limitations on document size, number of styles, and other parameters
• Processing complexity — automatic processing and data extraction from DOC requires specialized libraries

Compatibility with Modern Software

Although most office suites still open DOC files, working with them comes with limitations:

• Compatibility mode — Microsoft Word opens DOC in a special mode with limited functionality
• Lost features — new Word capabilities (improved formatting, new chart types, modern styles) are unavailable
• Error risk — when editing and saving back to DOC, some elements may be lost

Security

The DOC format has historically been a vector for malware distribution:

• Macro viruses — DOC supports embedded VBA macros that were used to create viruses
• Exploits — due to the complex binary structure, vulnerabilities were regularly discovered in DOC parsers
• Recipient distrust — many organizations block or warn about DOC files for security reasons

Comparison of DOC and DOCX Formats

Understanding the differences between formats helps evaluate the benefits of conversion:

The key architectural difference: DOC is a monolithic binary file, DOCX is a structured archive. If a DOCX file is partially damaged, you can extract undamaged XML files and recover some content. With a DOC file, this is virtually impossible.

When DOC to DOCX Conversion is Necessary

Updating Corporate Document Archives

Many organizations have accumulated extensive archives of DOC documents over years of operation:

• Internal documentation — regulations, instructions, provisions created in the Office 2003 era and earlier
• Contracts and agreements — legal documents that need to be stored for a long time
• Document templates — forms, templates, standard documents used as a basis for new ones
• Technical specifications — product descriptions, project documentation

Converting to DOCX ensures compatibility with modern document management systems, simplifies search and automatic processing, and reduces the risk of data loss due to file corruption.

Working with Legacy Documents

When receiving documents from external sources, you often have to work with the old format:

• Documents from government agencies — some institutions still use outdated software
• Materials from contractors — partners may be working on old versions of Office
• Historical materials — documents from archives created many years ago
• Documents from former employees — files left by previous workers

Conversion allows you to edit these documents in modern programs without compatibility mode limitations.

Preparing Documents for Editing

If you need to seriously rework an old document, converting to DOCX opens access to modern tools:

• Collaboration — DOCX supports review mode and collaborative editing in cloud services
• New formatting features — themes, improved styles, new types of charts and graphs
• Integration with modern systems — document management, CRM, ERP systems work better with DOCX
• Automation — scripts and macros are easier to apply to DOCX XML structure

Migrating to New Software

When transitioning to new versions of office suites or alternative solutions:

• Updating Microsoft Office — new versions of Word are optimized for DOCX
• Moving to cloud solutions — Microsoft 365, Google Docs work better with modern formats
• Using alternative suites — LibreOffice, WPS Office provide better DOCX compatibility

What is Preserved During DOC to DOCX Conversion

Conversion ensures transfer of all main document elements:

Text and Formatting

• Text content — all document text is transferred completely
• Fonts and sizes — font names, sizes, styles (bold, italic, underline) are preserved
• Colors — text color, highlighting, paragraph background
• Paragraphs — indents, spacing, alignment
• Lists — numbered, bulleted, multilevel lists

Structural Elements

• Headings and styles — heading hierarchy, custom styles
• Headers and footers — top and bottom headers, page numbering
• Footnotes — page and endnotes
• Table of contents — auto-generated table of contents (requires updating after conversion)
• Bookmarks and links — internal links, hyperlinks

Tables

• Structure — rows, columns, merged cells
• Formatting — borders, fill, alignment
• Content — text, numbers, nested elements
• Auto-fit — column width settings

Graphic Elements

• Images — embedded pictures, photos
• Shapes — autoshapes, lines, arrows
• Charts — graphs created in Word
• WordArt objects — decorative text
• Text wrapping — position settings relative to text

Conversion Features and Possible Nuances

In most cases, DOC to DOCX conversion produces results identical to the original. However, there are a few points worth knowing:

VBA Macros

DOC documents may contain macros — program code in Visual Basic for Applications:

• Simple macros — are converted and remain functional
• Complex macros — may require modification due to differences in object models
• Security — modern versions of Office require explicit permission to run macros

If the document contains critically important macros, it is recommended to test them after conversion.

Embedded OLE Objects

DOC supports embedding objects from other applications (Excel tables, PowerPoint presentations):

• Linked objects — links to external files are preserved
• Embedded objects — are transferred with the document
• Editing — editing capability depends on installed programs

Specific Formatting Elements

Some rarely used features of old Word may be handled specially:

• Text boxes — are converted to modern text fields
• Forms — form fields are transferred but may require verification
• Text effects — outdated effects are replaced with modern equivalents

Alternatives to Online Conversion

Microsoft Word

If you have Microsoft Word installed, direct conversion is possible:

1. Open the DOC file in Word
2. Select "File" → "Save As"
3. Choose "Word Document (*.docx)" format

Disadvantages: requires a license, each file must be processed manually.

LibreOffice

The free office suite also converts DOC to DOCX:

1. Open the file in LibreOffice Writer
2. Select "File" → "Save As"
3. Choose "Office Open XML (.docx)" format

Disadvantages: requires program installation, manual processing of each file.

PEREFILE Online Service

Advantages of converting through PEREFILE:

• No software installation — works directly in the browser
• Fast processing — no need to wait for heavy office suite loading
• Accessibility — works on any device with internet
• Batch processing — can convert multiple files

Who Needs DOC to DOCX Conversion

IT Specialists and System Administrators

Mass document migration task during infrastructure updates: transitioning to new Office versions, implementing document management systems, setting up backup. Online conversion simplifies processing individual files identified during migration.

Secretaries and Office Managers

Daily work with incoming documents from various sources. When receiving a DOC file, you can quickly convert it to modern format for further work without compatibility mode limitations.

Archivists and Document Management Specialists

Bringing document archives to a unified format, preparing for migration to electronic archives, ensuring long-term document preservation. DOCX as an open standard is preferred for archival storage.

Lawyers and Contract Specialists

Working with old contracts, addenda, standard forms. Conversion allows using modern review and document comparison tools.

Teachers and Methodologists

Updating educational materials, methodological guides, work programs created many years ago. After conversion, you can use modern formatting and design capabilities.

History of Word Formats

The DOC Era (1983-2007)

The DOC format appeared with the first version of Microsoft Word in 1983. Over 24 years of existence, it underwent many changes:

• Word 1.0 (1983) — first version of the format
• Word 6.0 (1993) — format unification for DOS, Windows, and Mac
• Word 97 (1997) — last major revision, "Word 97-2003" format
• Word 2003 (2003) — last version with DOC as default

The DOC format became the de facto standard for document exchange, despite its proprietary nature. However, the closed specification created problems for third-party developers and users of alternative platforms.

Transition to DOCX (2007-present)

In 2007, Microsoft introduced the new Office Open XML format:

• Office 2007 — DOCX became the default format
• ISO 29500 (2008) — OOXML approved as international standard
• Office 2010-2021 — further format development
• Microsoft 365 — cloud work with DOCX

The transition to an open standard provided better compatibility between programs, simplified automatic document processing, and improved storage reliability.

Recommendations for Quality Conversion

Preparing the Source File

Before conversion, it is recommended to:

• Check integrity — ensure the DOC file opens without errors
• Save a backup — in case you need to return to the original
• Clean metadata — if personal information needs to be removed

Checking the Result

After conversion, you should check:

• Text and formatting — ensure main content transferred correctly
• Tables — check structure and data in tables
• Images — ensure pictures are in place and in required quality
• Numbering — check page, section, and list numbering

Further Work with the Document

The converted DOCX file is ready for full use:

• Opens in any modern version of Word without limitations
• Supports all modern formatting features
• Compatible with cloud services (OneDrive, SharePoint, Google Drive)
• Suitable for collaborative editing