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How to stream large .mp4 files?

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Streaming large video files from the server to the client which might be a web app or mobile apps inefficient manner! 

We can’t send the entire video once to a client. because there are conditions like the bandwidth and data restrictions of the user.


Let’s say youtube, the user may watch some part of the video and went away for some reason, if he opened that video again, it should not load the entire video from start. 

Here is the part we need some mechanism to handle this situation. 

Nodejs stream API comes into the picture, its more efficient than reading a file in a conventional manner and waiting for the callbacks to resolve.

Created a basic video streaming server to explain it little better.  

The flow of the system:

  • User visits the site (index.html)
  • The html5 video component in index.html is pointed to URL of the video that is streaming by server
  • The video request is handler by the server by processing range header and sends out part of the video as partial content

Setting up project:

  • Open terminal
  • mkdir <project name>
  • cd <project name>
  • npm init -y
  • Open your favourite  text editor
  • Create index.html on that folder (check below html code, use it there)
  • Create a server.js file(check the js code provided below)
  • Run the command “node server.js”
  • Open browser and navigate to “localhost:3000”

Complete source code:

We will need a index.html file show the video that coming from the server!


<!DOCTYPE html>
<html lang="en">
    <meta charset="UTF-8">
    <meta name="viewport"
    <meta http-equiv="X-UA-Compatible"
    <title>video player</title>
    <video src="http://localhost:3000/video" controls>



const http=require('http');
const fs=require("fs");
const path=require("path");
/* http.createServer takes a handler
   function and returns a server instance;*/
const server=http.createServer((req, res)=>{
    // return res.end(req.url+req.method);
    if(req.method==='GET' && req.url==="/"){
        /*we will send a index.html page when
          user visits "/" endpoint*/
        /*index.html will have video component
          that displays the video*/
    //if video content is requesting
    if(req.method==='GET' && req.url==="/video"){
        const filepath = path.resolve("video.mp4");
        const stat = fs.statSync(filepath)
        const fileSize = stat.size
        const range = req.headers.range
        /*when we seek the video it will put
          range header to the request*/
        /*if range header exists send some
            part of video*/
        if (range) {
            //range format is "bytes=start-end",
            const parts =
                range.replace(/bytes=/, "").split("-");
            const start = parseInt(parts[0], 10)
            /*in some cases end may not exists, if its
                          not exists make it end of file*/
            const end =
                 parts[1] ?parseInt(parts[1], 10) :fileSize - 1
            //chunk size is what the part of video we are sending.
            const chunksize = (end - start) + 1
            /*we can provide offset values as options to
           the fs.createReadStream to read part of content*/
            const file = fs.createReadStream(filepath, {start, end})
            const head = {
                'Content-Range': `bytes ${start}-${end}/${fileSize}`,
                'Accept-Ranges': 'bytes',
                'Content-Length': chunksize,
                'Content-Type': 'video/mp4',
            /*we should set status code as 206 which is
                    for partial content*/
            // because video is continuously fetched part by part
            res.writeHead(206, head);
        //if not send the video from start.
        /* anyway html5 video player play content
          when sufficient frames available*/
        // It doesn't wait for the entire video to load.
           const head = {
               'Content-Length': fileSize,
               'Content-Type': 'video/mp4',
           res.writeHead(200, head);
    /*if anything other than handler routes then send
      400 status code, is for bad request*/
        res.end("bad request");
/*check if system has environment variable
   for the port, otherwise defaults to 3000*/
const PORT = process.env.PORT || 3000;
//start the server
server.listen(PORT, () => {
  console.log(`server listening on port:${PORT}`);


Finally we can see the result in the browser

Final Result

Last Updated : 28 Jul, 2021
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