What is the difference between fs.readFile and fs.createReadStream

Short answer

fs.readFile loads the entire file into memory before invoking the callback, while fs.createReadStream reads the file incrementally in chunks, making it far more memory-efficient for large files.

Key differences

• Memory usage: readFile buffers the whole file. createReadStream uses a small internal buffer and emits data chunks.
• Timing: readFile provides the complete data at once. createReadStream allows processing to begin before the entire file is read.
• Use case: readFile is convenient for small configuration files. createReadStream is essential for large logs, media files, and data pipelines.

When to use each

• Use fs.readFile when the file is small and you need the entire content immediately.
• Use fs.createReadStream when the file may be large, when piping to another stream, or when you want to start processing data as soon as possible.