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The carbon footprint of watching Netflix periodically invitations knowledgeable third events to share their views on the trade’s most urgent points. On this piece telecoms engineer Natalia Molinero Mingorance seems to be on the environmental implications of the video streaming revolution.

Video streaming is extensively utilized in many areas resembling leisure, social media, and on-line schooling. The consumption of video has dramatically elevated over the last decade, recently accelerated with the deployment of 5G which permits us to remain related at any time and in any location. The truth is, Web Service Suppliers have reported that a couple of third of their community visitors is Netflix. It has greater than 200 million subscribers worldwide in over 200 international locations.

On this article, we’re going to analyze what occurs after we watch motion pictures and TV reveals on the favored platform. The purpose is to grasp the way it works so we are able to pay attention to the carbon footprint of our on-line habits. How? By analyzing the computational complexity of processing video. Out there literature (together with publications made by Netflix itself) reveals that the video encoding and encryption strategies are essentially the most vitality demanding duties.

Netflix behind the scenes

What does it occur after we watch an episode of our favourite episode on Netflix?

First, that video file needs to be correctly saved someplace. Content material suppliers (e.g., video manufacturing firms) add a duplicate of the film to a server; that is the Origin Storage or Central Place within the Netflix Content material Supply Community (CND). The unique video in a high-definition format (with no compression) can have a measurement in terabytes. Truly, to get an concept of the storage necessities, picture that:

  • The common variety of movies reproduced by a person per day is 5
  • The common measurement of a film is 1 GB
  • The common variety of movies uploaded per day by content material creators to this backend is 1,000

Due to this fact,

  • The overall add storage required per day is 1,000 * 1 GB = 1 TB (roughly)
  • The overall storage required within the Central Place of the CDN for five years is 1 TB * 5 * 365 = 1.8 PB

These are fairly conservative numbers, as Excessive-Definition motion pictures with out compression can weight greater than 1 GB.

They use Amazon Internet Providers (AWS) for nearly the whole lot besides streaming. That features on-line storage, advice engine, video transcoding, databases, and analytics.

Processing the video

Netflix helps greater than 2000 gadgets and every requires completely different resolutions and codecs. After including some meta information to manage content material administration operations (title of the film, class, licensing…), the video is encoded for various qualities, so it may be reproduced with completely different bandwidths, relying on the person gadget (PC, TV, smartphone) or the community necessities. To realize this, Netflix breaks the unique file into completely different smaller chunks and, utilizing parallel employees in AWS, it converts these chunks into completely different codecs (like mp4, 3gp, and so on.) throughout completely different resolutions (like 4k, 1080p, and extra).

A configuration file (“manifest file”) is produced to inform the encoder the parameters that needs to be utilized for encoding.

These completely different technical options on the flicks are achieved utilizing audio and video codecs.

This fashion, an instance of what Netflix usually shops in a kind of nodes are the movies representations similar to the mixture of:

  • 10 resolutions to permit for bitrate adaptation to the terminal
  • 4 codecs, relying on the terminal the video is performed on (VC1, H.264/AVC Baseline, H.264/AVC Predominant and HEVC)
  • 3 ABR applied sciences (HLS, Easy Streaming and DASH), so as, additionally, to deal with completely different terminals.

This results in 120 representations of the identical film with the purpose of streaming it to greater than 900 completely different gadgets

After these operations are run within the AWS servers, the content material is DMR coded, i.e., encrypted, and solely customers that paid for it will possibly watch it.

Determine 1. CDN structure, by Rafael Mompó

Copying the video in several places

Subsequent, all variations of the content material (one for every sort of gadget and for every picture high quality) are uploaded to a tough disk (regional origin server or Management Place on the CDN) to be distributed. By means of Safe FTP, the recordsdata are obtained on the CDN Entry Level or Central Place. Due to this fact, motion pictures are normally ingested within the Management Place. The Central Place shops a “grasp” copy of them and retains details about these which are saved in all regional nodes and the way busy the nodes are (sometimes, there’s visitors overflow from one area to a different). Open Join is the Netflix CDN, a community of distributed servers unfold throughout completely different geographical places, answerable for streaming.

As we’ve seen, all motion pictures are saved within the Central Place of the of the CDN, however a duplicate of the film is saved in a Node nearer to the customers after they request it. These nodes retailer the movies within the completely different codecs in keeping with the gadget or sort of companies (PC internet browser, Good TV, Android APP….). The extra customers requesting a video, the extra nodes needs to be in a given area. After sure time, if customers don’t request it, it’s deleted. These nodes are in command of:

  • Obtain administration: test if the video is saved regionally. In any other case, it downloads it from the Management Place, from the Central Place or from one other one nearer neighborhood node.
  • Neighborhood administration: it maintains a listing of all contents which are out there on the nodes which are nearer
  • Streaming server: controls that the assigned bandwidth to a sure person is throughout the configured limits
  • Storage administration: it deletes motion pictures when the disk is close to to be full, however earlier than deletion, it checks that there’s not a person taking part in that content material
  • Geo-blocker: checks if the person IP corresponds to a rustic that’s allowed to observe the video, since content material licensing is given by nation

To have motion pictures/reveals in nearer nodes, proxies will be positioned between nodes and the regional origin server.

A fast abstract until this level: while you hit the play button, Netflix analyzes the community velocity or connection stability. Relying on the gadget and display measurement, the appropriate video format is streamed into the person’s gadget. The film will probably be served to the person from the closest Open Join server which results in sooner and higher expertise. This additionally will increase the scalability of the entire system.

Storage Capability

Netflix makes use of Cassandra for its scalability and lack of single factors of failure and for cross-regional deployments. A single international Cassandra cluster can concurrently service functions and asynchronously replicate information throughout a number of geographic places.

Cassandra information mannequin in Netflix is constructed with the next components:

  • Greater than 50 Cassandra clusters
  • Greater than 500 nodes
  • 30TB day by day backups
  • 250k Writes/s at every node

The price of watching on-line video: Netflix aspect

As you’ll be able to think about, Netflix should have a number of kilometers of knowledge facilities to maintain these servers. Due to this fact, powering these servers operating 24/7 for video processing and storage is pricey and, even when they use inexperienced electrical energy in some, the remainder of them can have tons of related inexperienced home gasoline (GHG) emissions. Truly, Netflix has reported being accountable of greater than 6 billions of grams CO2 final 12 months.

The next picture reveals the useful scheme of the weather which are within the Netflix aspect:

Determine 2. Netflix CDN structure

The video headend is the place the unique file is uploaded and ready earlier than sending it to the servers within the CDN. The encoding and decoding duties are essentially the most vitality demanding. To avoid wasting vitality, the transcoding is finished as shut as attainable to the person, so it’s carried out on demand-basis as an alternative of getting a number of variations of the identical file already processed and saved. The goal is to avoid wasting vitality from computing time and feed the servers for storage. Let’s check out the costliest operations:

As we are able to see within the image above, the video frames are delivered to us due to the streaming protocols. These protocols will be within the three layers of the OSI mannequin: Software, Presentation and Session layer. Some examples are Adobe Actual-Time Massaging Protocol (RTMP), MPEG-DASH, Apple HTTP Stay Streaming Protocol (HLS), and the ever used, QUIC which relies on UDP and depends within the transport layer. Every of those protocols is appropriate for sure sorts of video containers, i.e., MP4, which is broadly used as a result of it’s suitable with a variety of gadgets. The protocols are additionally outlined for particular video codecs, being H.264, H.265, and VP9 the commonest.

Compression is important earlier than storing or transmitting the video. We’ve checked the encoding utilized by Chrome whereas watching a present in Netflix:

Determine 3: Chrome video gamers for Netflix

Determine 4: Video transcoding strategies on Chrome whereas reproducing Netfix

Due to this fact, it’s VP9, a compression license-free commonplace primarily outlined by Google.

These streams go over a TLS/SSL connection to guard the communications with encryption, usually, completely different AES-based strategies. AES is a block-based cypher which was first printed in 1998. The blocks have a set measurement of 128 bits and the important thing will be 128, 192 or 256 bits. That is an extensively accepted cypher as a result of it’s open supply and the {hardware} necessities by way of storage and processing time are comparatively low. As well as, it’s straightforward to implement. As talked about, QUIC is a transport protocol extensively used and it contains encryption. One other streaming protocol, RTMPS, depends on a TLS/SSL connection which additionally ensures the streaming safety by way of encryption. We’ve seen these protocols whereas capturing the Netflix visitors with Wireshark:

Determine 5. Video protocols for Netflix

These protocols are utilized by the platforms beneath examine, and all are primarily based on AES. As well as, we now have analyzed the web visitors whereas watching the present to double-check the encryption scheme they use: AES-128 CGM, as proven in Determine 6.

Determine 6. Encryption scheme utilized by Netflix

Encrypting video information leads to a better stage of safety, nevertheless it additionally produces extra computational complexity, and it prices extra time.

Whereas compressing and encrypting a textual content file is comparatively easy, video compression and encryption are extra complicated, as computations should be carried out on plenty of megabytes of knowledge which are constantly saved, retrieved and transferred from information facilities and end-user gadgets. This computational value leads to vitality consumption. Because of this, the way to get steadiness between compression, safety and time-energy effectivity is a crucial goal to realize a sustainable method of having fun with on-line video.

The price of watching on-line video: vitality consumption at dwelling

We’ve measured the ability consumed on a laptop computer and a TV whereas reproducing Netflix. The laptop computer is an Acer Aspire F 15 and the TV is a LED Samsung Good TV of 32’’.

All the ability values reported listed below are the common energy measured throughout 5 minutes of video. The TV consumption when off was 13.7 W, whereas the laptop computer didn’t eat vitality when turned off. The worth of electrical energy in Spain the day of the assessments was 0.20341 €/kWh. Tables 1 and a couple of present the outcomes of the consumed energy values and the worth of taking part in these 5 minutes of our favourite present on the laptop computer and on the TV.

Laptop computer (W) TV (W)
IDLE 7.2 25.5
Watchig video 15.6 45.13

Desk 1.- Energy consumption of a laptop computer and a TV when idle and when watching Netflix.

Laptop computer (€) TV (€)
IDLE 0.00012 0.00043
Watchig video 0.00026 0.00077

Desk 2.- Financial value of when watching Netflix on a laptop computer and a TV.

As you’ll be able to see, streaming 5 minutes of Netflix on a TV (the costliest gadget between the 2 examined) is comparatively low-cost. In a 12 months, if we watch 2 hours of content material day by day, you must multiply the month-to-month subscription value by 12 and add 6.7 € for the electrical energy consumption.

Related carbon footprint

Perhaps the financial value is low however let’s check out this: in keeping with, the era of 1kWh produces 0.371 kg CO2. If taking part in 5 minutes of video consumes 45.13 W and we contemplate we watch 2 hours day by day, in a 12 months, that may be 33 kWh yearly, which is 12.2 kg CO2 produced by every of us only for streaming on-line content material.

In Spain, there are roughly 19,000,000 household homes. If Netflix is watched a median of two hours in every home, the yearly air pollution generated by reproducing Netflix on TV, contemplating that the 40% of the vitality in Spain is generated with renewable sources, is 139.1 kt grams of CO2. Thus, perhaps we don’t even discover the electrical energy prize as a consequence of Netflix in a 12 months however the planet actually does.


Whereas each time extra firms like Netflix are investing in renewable energies for his or her information facilities and CDNs, this isn’t a whole answer, because the inexperienced vitality remains to be costly and troublesome to entry in some international locations and never all of the processes because the stage when the video is created until it reaches our screens use this renewable sources. Truly, most customers have conventional (for example, gasoline generated) vitality at dwelling, producing dozens of kg of GHG emissions day by day, as within the case of Spain.

As we now have seen, on the server aspect, the Netflix CDNs and information facilities consist in very highly effective servers storing and processing giant volumes of video. Equally, the height on the vitality consumption that we noticed in our laptop computer and TV is as a result of video encoding algorithms that require a lot computational load to run, particularly compression algorithms (really, rather more than encryption).

Whereas video compression strategies are required to cut back the capability and the variety of servers, at current, there’s a trade-off between the compression charges and the computational energy required to realize a considerable discount: the larger the compression, the extra assets are wanted. Due to this fact, there’s a have to design lighter algorithms with the goal of:

  • Acquiring excessive qualities movies
  • Utilizing minimal computing assets
  • Lowering the vitality consumed

Concord Valley is a analysis mission devoted to design these algorithms for the brand new and required paradigm of a sustainable digital world, so everybody can take pleasure in essentially the most superior applied sciences with out hurting the planet.


I’m Natalia Molinero Mingorance, a Telecommunications engineer and MSc. in Wi-fi Communications Techniques. I labored within the College of Sheffield (U.Ok.), as a researcher, and I additionally labored in trade, offering companies to the principle European telecom carriers. In April 2022, I used to be awarded the primary prize in a contest run by the European College of Madrid (Spain), the “Singular Alumni”, for my mission proposal “New Strategies for Vitality Effectivity Optimization: Data, era, storage, transmission and reception”, which is the primary stage of Concord Valley. Concord Valley is a analysis mission (anticipating to be an R&D firm) whose important purpose is to contribute to creating digital communications sustainable. On this first stage, the analysis is concentrated on discovering new video compression algorithms to save lots of computing energy. The long-term purpose is to supply new strategies and options to the completely different requirements our bodies (radiocommunications, community protocols, and so on.) and multimedia non-public firms, so vitality consumption is a parameter as necessary as high quality when designing a brand new know-how. I created a social media profile so as to make the analysis and the subjects that addresses accessible by everybody (


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