When developers compare files with identical content but notice that their sizes differ, it can be perplexing. Let’s explore why this happens and what factors influence the size of files with extensions like *.js, *.php, and *.css.
1. File Encoding
One of the key factors affecting file size is text encoding. The most common encodings are:
- UTF-8 — widely used in web development. ASCII characters occupy 1 byte, while special characters take up more.
- UTF-16 — characters occupy 2 bytes or more, increasing file size.
- Windows-1251 — used for Cyrillic texts and takes up less space for Cyrillic characters compared to UTF-8.
If two files have the same content but different encodings, their sizes will differ.
2. Line Ending Characters (CR, LF, CRLF)
Line ending characters also impact file size. Different operating systems use different standards:
- Linux and macOS: LF (1 byte).
- Windows: CRLF (2 bytes).
If one file is created on Windows and another on Linux, their sizes will differ even if the content is the same.
3. File Metadata
Every file contains service information stored in the file system. This information may include:
- Timestamps for creation, modification, and access.
- File attributes (e.g., permissions).
- BOM (Byte Order Mark) in text files.
For instance, files with BOM may be slightly larger.
4. Minification and Compression
Some editors or systems automatically compress file contents. This is especially relevant for JavaScript (.js) and CSS (.css) files, which may be:
- Minified (removing spaces, line breaks, and comments).
- Compressed using algorithms like gzip or Brotli during server transmission.
PHP files usually contain server-side code and are not subject to minification, which can also affect their size.
5. File System and Alignment
On a physical level, files are stored in blocks of the file system. The size of these blocks affects the minimum file size:
- For example, if the block size is 4 KB, a file that is 1 KB will still occupy 4 KB on the disk.
- Different file systems (NTFS, ext4, FAT32) use their own alignment algorithms.
6. Differences in File Structures
Each file type has its own characteristics:
- PHP files may contain more metadata, such as embedded
<?php ?>
tags, comments, or interpreter instructions. - CSS files are usually smaller because they represent a set of styles without additional code.
- JS files often contain executable code, which may be minified to reduce size.
How to Check and Eliminate Size Differences?
- Check the Encoding. Ensure all files use the same encoding, such as UTF-8 without BOM.
- Unify Line Endings. Use tools like Prettier or EditorConfig.
- Minify Files. For CSS and JS, use tools like Terser or PostCSS.
- Review Metadata. Remove unnecessary attributes or temporary data if possible.
- Analyze the File System. Ensure block sizes meet your requirements.
Conclusion
Differences in file size with identical content can be caused by many factors: from encoding and line endings to file system characteristics and file structures. Understanding these nuances will help you optimize file handling and improve performance in web development.
Keywords: file size, file encoding, CSS and JS optimization, line endings, file minification, PHP files, file system, web file optimization, file weight, different file sizes, UTF-8, CRLF, BOM.