File Merger Tool
Merge PDF files, Word documents, Excel spreadsheets, and data files online with advanced options for page selection, bookmarks, and formatting preservation.
Choose File Type
Select the type of files you want to merge
PDF Files
All pages combined in order, bookmarks preserved
DOCX Files
Documents combined with page breaks between files
XLSX Files
Excel spreadsheets merged with all columns combined
Text Files
All text content combined line by line (supports .txt and .md)
CSV Files
All columns combined, empty cells where data missing
JSON Files
Lists combined, objects merged together
XML Files
Documents intelligently combined
Professional file merger tool supporting PDF, Word, Excel, CSV, JSON, and text files with advanced format preservation. All processing happens locally in your browser using WebAssembly for complete privacy and security - no server uploads required.
How It Works
Choose File Type
Select the format you want to merge: PDF, Word, Excel, CSV, JSON, XML, or text files.
Upload Your Files
Drag and drop or browse to upload multiple files of the same type to merge.
Configure Options
Review your files and adjust merge settings for optimal results.
Merge Files
Our tool intelligently combines your files while preserving structure and formatting.
Download Result
Get your merged file with all content combined according to the format specifications.
Features
PDF File Merging
Combine multiple PDF files into a single document while preserving page order and automatically maintaining bookmarks using pdf-lib
Excel Spreadsheet Merging
Advanced sheet-by-sheet merging with column union strategy. Sheets with same names are intelligently combined, preserving data and basic formatting
Word Document Combining
Merge DOCX files with automatic page breaks between documents. Preserves formatting, styles, and embedded content
CSV Data File Merging
Smart column union merging that handles different CSV structures, quoted fields, and missing data with proper CSV parsing and escaping
JSON File Combination
Intelligent JSON merging: arrays are concatenated, objects are merged by property, mixed types are wrapped in arrays
Client-Side Processing
All file processing happens in your browser using WebAssembly and JavaScript libraries. No files uploaded to servers for complete privacy
Smart Memory Management
Built-in limits prevent browser crashes: 50K rows/1K columns per Excel sheet, 100MB total file size, with progress tracking
Drag & Drop Interface
Intuitive file upload with reordering support, real-time validation, and instant preview of merge structure before processing
Frequently Asked Questions
How to merge PDF files online for free?
Upload multiple PDF files and our tool combines them into a single document while preserving page order, bookmarks, and formatting. PDF merging follows ISO 32000 PDF specification standards. The entire process happens in your browser using PDF-lib for complete privacy - no files are uploaded to servers.
What file formats can I merge together?
Supported formats include PDF documents, Word files (DOCX following ECMA-376 standard), Excel spreadsheets (XLSX), CSV data files (RFC 4180 compliant), JSON files (RFC 8259 specification), XML documents, and plain text files. Each format uses specialized merging algorithms optimized for that file type.
What are the file size limits for merging?
File limits are designed for optimal browser performance: PDF/Word files up to 25MB each, Excel files up to 25MB, CSV/JSON/XML up to 10MB each, text files up to 5MB. Total combined size cannot exceed 100MB. Excel files are limited to 50,000 rows and 1,000 columns per sheet to prevent browser memory issues while maintaining Excel compatibility standards.
How does Excel spreadsheet merging work?
Excel files are merged using a sophisticated sheet-by-sheet strategy following Microsoft XLSX format specifications. Sheets with identical names are combined using column union logic (all unique columns from both sheets). Sheets with unique names are copied directly. The merger preserves data and basic formatting but removes charts, pivot tables, and macros for compatibility.
How secure is client-side file merging?
Your files never leave your browser, ensuring maximum security and privacy. All processing happens client-side using WebAssembly and JavaScript libraries. Files are not uploaded to any server, providing complete data protection and faster processing without server-side file size restrictions. This approach follows modern web security best practices.
Can I merge CSV files with different columns?
Yes! CSV merging uses column union strategy following RFC 4180 CSV format specification - all unique column headers from all files are included in the result. Missing data is filled with empty cells. The tool handles quoted fields, escaped commas, and different CSV dialects automatically while maintaining data integrity.
How does JSON file merging work?
JSON merging follows RFC 8259 JSON specification with intelligent logic: Arrays are concatenated together, Objects are merged by combining properties (last value wins for duplicate keys), Mixed types are wrapped in a parent array. The output maintains valid JSON structure with proper formatting and adheres to JSON Schema standards.
What happens to Word document formatting when merging?
Word documents are merged with automatic page breaks between files following ECMA-376 OOXML standards. Original formatting including fonts, styles, headers, footers, and embedded images are preserved. However, complex features like track changes, comments, and document variables may not be fully maintained due to Office file format complexity.
Can I reorder files before merging?
Yes, the interface includes intuitive drag-and-drop reordering using modern HTML5 Drag and Drop API. You can change file order, remove unwanted files, and preview the merge structure before processing. The final output follows your specified file sequence, ensuring complete control over document organization.
What are the limitations of file merging?
Key limitations include: Only same-type files can be merged (no mixing PDF with Word due to format incompatibility), Complex Excel features (charts, macros, pivot tables) are not preserved following Excel web compatibility guidelines, Very large files may cause browser memory issues, PDF bookmark customization is automatic only. For best results, use files with similar structures and formats.
How to combine multiple text files online?
Text files are merged line-by-line in your specified order with automatic encoding detection supporting UTF-8 (RFC 3629) and other common encodings. Each file's content is separated by line breaks following Unicode text format standards. The tool handles different text encodings and removes unnecessary whitespace while preserving original content structure.
Does the file merger work offline?
Once the page loads, most merging operations work offline since processing happens entirely in your browser using modern web technologies. You need an initial internet connection to load the tool and its JavaScript libraries, but no ongoing connection is required during file processing, ensuring privacy and functionality in low-connectivity environments.