---
title: Record your screen and save with Rails active storage
slug: record-your-screen-and-save-with-rails-active-storage
published_at: 2021-06-19 19:21:13 +0000
updated_at: 2026-03-04 20:14:08 +0000
summary: 
description: #rails #rubyonrails
tags: []
views: 920
author: CJ Avilla
url: https://www.cjav.dev/videos/record-your-screen-and-save-with-rails-active-storage
youtube_url: https://www.youtube.com/watch?v=i_NEx7LwIAQ
youtube_id: i_NEx7LwIAQ
embed_url: https://www.youtube.com/embed/i_NEx7LwIAQ
thumbnail_url: https://i.ytimg.com/vi/i_NEx7LwIAQ/hqdefault.jpg
type: video
---

# Record your screen and save with Rails active storage

*Published: June 19, 2021*
*Views: 920*

## Watch

[Watch on YouTube](https://www.youtube.com/watch?v=i_NEx7LwIAQ)

[![Record your screen and save with Rails active storage](https://i.ytimg.com/vi/i_NEx7LwIAQ/hqdefault.jpg)](https://www.youtube.com/watch?v=i_NEx7LwIAQ)

## Description

#rails #rubyonrails

## Transcript

hey welcome back in this episode we're going to build out a small application for doing some simple screen recordings we're going to use some javascript apis to record some screens and then we will store that footage as uh as blobs in active record with active storage so let's get started so we're going to say rails new um let's call it uh hmm record my screen and we'll skip tests and we'll set the database equal to postgres and we will also skip turbo links and that should get us started okay all right while that's downloading i'm going to open up a couple more tabs here and in another tab i'm going to jump into that record my screen directory and i'm going to uh let's see this will be our pane for running the rails server so let's also split this vertically and go into that record my screen and we will we'll use this right hand side for running the webpack dev server i need to set my lo my local node and um to 10.17.0 so that i can actually use webpacker okay this thing is still installing so that's fine this is going to be dot slash bin slash web webpacker webpack dev server and then this side is going to be rails server once this all starts once this all finishes so the idea will be that we're going to create a model and store it in the database called record or recording um all right so it looks like that finished so cd record my screen and then we'll have a view where you can um or you can start stop and then save a recording so that's the that's the goal for today so that's what i think we're going to try to build out all right so let's start our rail server let's start our webpack dev server and we want to say like rake db uh create db migrate all the stuff we do at the beginning of every single rails app that we start up all right so now we've got the database right migrated let's set up the active storage so we have to say rails active storage colon install that's going to create a migration which will add tables to our database for storing like the blobs and those are going to be like polymorphically associated to objects so when we say rails g model recording we actually just need to give it likes the fields that are not related to the actual file so in this place in this case i'm going to give it a key the key will be some like unique identifier so we can maybe send a link to the recording so someone could navigate directly to like uh slash recording slash key and then that would fetch their recording so they could just you know do do a quick screen recording and then share a link to it all right so that will create a model in the database called recording let's go edit this create recordings migration really quickly we want the key to be non-nullable and let's give it an index also add index because we're going to look up the recordings by this key we want it to be a fast lookup and then we'll say unique true that'll also add a uniqueness constraint so we can say rakedb migrate and then in our recording model what we want to do is at uh we want to have a validation that says when the recording is saved we'll give it a key so we're going to say um before validation on create do and we're going to say self.key is equal to secure random dot oh i always forget what this is let's see rails let's see so i'm going to use the rails console to remember what the methods are on secure random okay so securerandom.methods.sort minusclass.new.methods and i think i want to use url safe base64 so this one and then i'll just pass in like four or something just to make it short and then the other thing we want to do in the recording is say has one attached and then we'll call the field file so by doing this has one attached it's going to create a polymorphic association between the stuff that's in the active storage database tables and the recording so the data doesn't actually live in the recording table it lives in the other table and then that other table references back to this it's magic i don't know how it works exactly but under the hood we're using active storage and all we have to do is add this one method here at the top to save a file with our recording so i think that should work and now we can say rails g controller recordings and we're going to have let's see we're going to have a route for creating a new recording we want to have a route for showing a recording and i think that should be good to start and this is actually going to be so simple that we're just going to have one route that's our route route and it's going to go to recordings uh new and then we'll have a get route to like slash r slash like id or something or maybe key yeah and that will go to uh recordings show that way we can say something like you know localhost 3000 slash r slash and then abc123 and that will pull up the recording for that that way it's just it's pretty short um but we still have like a little bit of a name space with that um with the slash r here all right so let's go to our recordings controller and in here in the new route we want to probably have a recording dot new just so we can fill something in if we wanted to use this on the form i'm not sure yet and then for the show route we want to find the recording recording is equal to recording dot find by params or like key rams key and that should look up the recording by that key and then we'll just build out a show page that will show the recording and then we also need a create action in here and this create action is going to create the new recording so this is going to be where we accept post requests and so we're going to say recording is equal to recording dot new recording params and then if we save that recording then we'll just render the json back for that recording because we're going to hit this endpoint with ajax i think else we want to render the json for at recording.errors.full messages and we need to create this recording params thing so um we'll say params.requirerecording.permit file because that file is what we want to pass in from the front end okay so i think our recordings controller is looking pretty good um let's head over to the front end and uh implement some of this stuff on the view so our recording new page it's going to say like record my screen um okay so what are we actually going to have here i think we'll have maybe a couple of buttons we need a button to start start button start and we're going to need a button to stop and then let's also add a button to um to save save btn save and i think that should get us pretty far with just three buttons there so we've got our servers running let's pull up a localhost three thousand and poke around let's see localhost three thousand so we should land okay cool record my screen this is exactly what we want start stop and save and then if we open up the console here let's uh let's go add some javascript now so in the javascript packs thing here i'm going to add a recording dot js so i'm going to add a brand new pack and i'm going to say um only run this when the dom is fully loaded and we're gonna grab reference to those buttons so uh start button start button um stop button stop button uh and the save button okay and then i'm gonna add click handlers for each of these and we'll just log out started stopped and saved all right let's go test those out so if we refresh the page here and we click start we don't see anything and that is because we haven't actually installed the javascript pack tag so i'm going to do this i'm actually going to install the pack tag directly on the new page so here i'm just going to add a oh gosh how does this work javascript pack tag for recording and the name of this matches this and the hope is that our webpack dev server is actually like picking up that file we might need to restart this thing because we started the devpak the webpack dev server before we created that recording pack so i'm restarting it and i think it should have picked it up i see recording something something here so now when we refresh the page we should have some javascript installed start start recording stop recording save recording okay so that is looking good now what we want to do is say when we start recording we actually need to do a couple of different things so the first part of this is to actually do some capture we want to do some capture of um of the screen and then the second part is we want to like record that capture so there's two there's two different steps so one is like getting access to the screen and then like creating a stream or some tracks from that stream and then the second part is using a media recorder to actually like collect up those tracks and then do something with the data as it's streaming in um so let's start off with maybe starting starting the capture so let's go over to our javascript here in the recording and we're going to create a new function down here um async function start capture start capture and i think this is going to return so this is going to like actually like get access to the screen and return um a stream okay so what does this actually look like const um let's see so this is going to be a string or like let stream let me need a try catch block and console.error e and then what we want to try is we want to try setting the stream equal to await navigator dot media devices dot get display media and we can pass in an object if we want with some arguments audio false that's like if you wanted to capture the audio of what's playing on the desktop screen so we don't actually want that audio or care about that audio so i think that's fine and then we'll just return the stream here and so in our start function uh we want to say like const or we want the stream back stream is equal to a weight start capture and then instead of creating a global variable here we'll make a let uh stream because we're going to want to pass that stream around for a couple other things so that should start the capture and then when we want to stop the capture down here we want to go let's call stop capture and this will be another function and this will take in the stream and we want to iterate over the tracks for the stream so we're going to say stream.gettracks.4 each and for each track we want to call stop on each track track.stop and that should stop the recording right so that is this is the i think this is the bare minimum for just like handling the capture piece for the screen so let's go back over here refresh the page and click start okay so now we get this dialog that asks us do we like which part of our screen we want to record a window or the whole screen or whatever so we can click share and now we have started sharing you can see this is a this tab is sharing your screen whatever and now we can hit stop and we have an error cannot read property get tracks of undefined because we didn't pass it in to stop capture stream okay so at that point i think we should be good to go let's try this again task test test stop okay so now we've got start recording and we've got stop recording so that is the capture piece now we need to do the recording piece of that capture so i think i actually want different functions for the recording piece so let's do uh async function start recording and we're going to pass again in i think we're going to pass in the stream here and what we want to do here for the recording is we want to create a media recorder from that stream and we want to start the media recorder and i think for start recording this is actually going to return the media recorder so const recorder is equal to new media recorder for the stream and i think i can't remember if we want to pass in any settings or anything to this but whatever this should this should get us at least going so recorder.start so that should actually start the recording for the given stream so then when we click the start button up here let's also say a weight um actually is this i don't know if that's actually i don't we'll see i don't know maybe we don't even need async here let's that's okay so we'll just say start recording and we'll pass in the stream all right so then when we call stop recording do we need to oh yeah so when we call stop recording we need to actually stop yeah we need to call stop recording and i i think we want to pass the recording in or the recorder so let's let's also keep track of the recorder here and when we call stop recording we'll pass in the recorder and we'll make a new function here stop recording and we'll take in the recorder and i think we want to call recorder.stop and i can't remember if there's anything else we're going to do in here probably uh yeah that that should be good i think so okay so that should stop the recorder um now what do we actually do with this data well as the recorder receives pieces of data it should get something like recorder.on data available and that's going to be a function that emits events as data becomes available and these events are going to have like event or like e.data they'll have blobs or i think they're like chunks of data and every time this on data available event fires on the recorder we want to collect up all those chunks and then ultimately when we save we want to pass those chunks down to the server we could be like streaming them down to the server or something but instead i think we'll just limit the uh the maximum duration for a recording and then we'll just keep everything sort of like in memory um and i think that should be fine so what we want to do with this is we actually want to add these to some array and i think we're going to need that array when we call save from this like upper class so let's actually call this chunks here and then we'll we'll pass it down when we start recording chunks and then when that event fires we're going to add that data into the chunks array so we'll say like chunks.push e.data and so that should modify the array and just keep adding to it as data is available which i think should work um okay so what we should do now is test and make sure this stuff is working so when we say stop recording why don't we just say let's console.log chunks and then we'll refresh this page and we'll say start recording record this screen over here and we're doing stuff we're doing stuff and then we say stop all right so we got chunks and it's an array that has a blob cool and it has a size and it's using this video codec so all of that looks cool all right so now what we want to do is take all of these chunks and when we click save we actually want to take all the chunks and create the create a file object and pass it down to the server using ajax so that we can create one of those recording objects so let's do that now so when we um when we call save we want to call maybe like uh const recording is equal to await save recording and we'll pass down the chunks let's come down here async function save recording and we'll take in the chunks and then what we want to do is we want to create a file um so file is new file we're going to pass in chunks and then we want to pass in a couple other arguments here so the type is going to be like the mime type for the file and i think we can use video slash webm and then we also want to pass a file name which can just be like uh recording.webm or something that i think that file name thing is a requirement for active storage um okay so then what we want to do is construct the form data that we're going to send to the back end so const form data is a new form data and form data.append and now the this is going to be like sort of that url encoded format so we want to pass in recording and then square brackets file so this is this is the top level key for the params and then file is going to be like nested inside of that hash and the value here is going to be that file object and then we can use the fetch api um whoops fetch it's going to be a post request and we're going to get back the recording we're actually just going to return oops the whole recording we'll make this a post request to slash recordings and i'm remembering that in our routes we don't actually have a route for that so post to slash recordings to record actually let's just say resources recordings because we might want to do other stuff too so all right we don't want to pass a content type but we do need to pass our csrf token um which we can get out of uh out of the page here so every time the page reloads you should get a csrf token so this is something that rails is doing for you on like automatically and so at the very top here notice that we have this meta tag that has the name csrf token and then the content here is what we actually want to pass as our csrf token in the xcsrf token header um i've i feel like back in the day ajax and uj rails ujs did like some of this for you but now that we're using the fetch api i i just like either i either skip often like uh skip the authenticity check which is bad practice or i will look up the csrf token so i think we can do like document.getelement by name or something get elements by name and then pass in csrf token and that gives us a node list so we want the first one and we want its content and that should give us the csrf token another way to do this is if you're in erb you can do something like authenticity uh token or something like that um rails authenticity token it's there's a there are there are like erb helpers to get this but because we're in javascript we don't have access to those um we're in like the javascript pack tag so we can't use um like erb or something right here or i mean we maybe we could but we're not going to cons token is equal to this thing so that's what we're going to pass down for the token and then we want to pass the form data as the body here i think the the content type we technically want to pass like multi-part form or something like that but i found that if we just leave the header out rails can figure out what we're passing down because we are passing a file so this is the save recording logic we're expecting to send a post request with that file that we just created based on the chunks that were recorded and then it should yeah um it should return a new recording object um okay so when it when we get back to here why don't we console.log recording all right so let's give this a whirl so we're going to refresh the page click start pick our screen all right we're recording we're recording and then we hit stop and we've logged out some chunks okay and then when we hit save we should make an api request to slash recordings to save that file all right so we made a post request we got a 200 back and in the in the console we're logging out that recording notice it has this key that was like randomly generated from secure random that's nice it doesn't actually have a file object on it which is totally fine but now what we want to do is go look in the rails server look at that active storage blob update okay so it looks like it may have actually saved some stuff so we've got a recording and yeah action dispatch uploaded file okay so this is all looking pretty good why don't we go see if that recording worked so let's go to recording show i'll just call it recording and then we want to use a video tag here video tag and it's going to require a url as like the source we're going to say url for at recording dot file so that should give us like the fully qualified url for the file um and yeah okay so let's see if we can go to that let's see what happened to our console here console oh no we lost our okay so let's real c recording dot last dot key that's what we want to look at all right so if we go to like slash r slash that key oh look at that okay cool so it pulled up our recording and it's massive so we got to fix the size so let's fix the size first so we're going to say size is um oh gosh what is it 680 by 4 60. i can't remember what what like the okay whatever that looks fine um and then we also want our controls so that we can push play all right look at that okay we hit play oh look at oh amazing okay you can see there's you can see the screen recording so this is this is uh this is it this is amazing this is what we wanted we're gonna go through the process of also recording our voice and there's a couple little tricks to it because uh in order to save that video file with the combined tracks of voice and the screen video input we need to we need to make some refactors to break out those different pieces and make sure they get passed in correctly so in order to refactor this what we need to do is split out our capture so start capture needs to be refactored a little bit because in addition to the screen the screens stream we also need some audio stream so what i want to do here is say like voice stream so we're going to add in a second stream here so voice stream is await navigator dot use or yeah media devices dot get user media i think and here we want to pass in video false because we don't want to capture camera or anything yet and then audio true and then instead of returning a stream here what i think we can do is well yeah so so we were returning the single stream that was um the result of the resolution of this promise and now what we could do is return the arrays of tracks but i think what we want to do is actually create a new media stream from the combinations of those tracks so we'll say const tracks is equal to stream.gettracks and voice stream dot get tracks this one also needs to be spread and then we'll return a new media stream of tracks and that should return a new media stream that we can use i think we can use everything else very similarly yeah so when we stop the capture we'll just iterate over all the tracks and stop them and then as we're recording we should be able to take in that media stream so i think this i think this might work that was actually a very small refactor but let's see if we can get that working so if we refresh the page and let's open the terminal and we click start we pick which screen we want to record so i'm picking this screen here and then um i think the very first time that you do this it's going to ask you if you want to use your audio i've done a few different um episodes about recording audio so i think it's already got that permission so here we see it's sharing our screen all right so if we click stop all right we've got some chunks and if we hit save those should be uploaded and now we have a new key here for recording so if we go to slash r slash that recording now now this is the moment of truth does it have audio let's see play oh amazing wow okay so that was actually way simpler than i expected all right so that is how you combine multiple different recordings is by by creating a new list of tracks and creating a brand new media stream which is the combination of all those tracks okay so yeah so now we have a working tool for creating recordings and saving them and then sharing a link directly to them in the next episode i think i'm going to go through the process of showing how to set up an active storage backend so that we can actually upload these files to some service and then um yeah and then we can publish this on heroku and have a little screen recording service so i think that's that's the next step you

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