What does buffering mean? | Buffering in video streaming

Buffering is a core part of how streaming works, but slow buffering can be frustrating for viewers. There are many potential causes of slow buffering, but fortunately, there are also several ways to improve its speed.

Learning Objectives

After reading this article you will be able to:

  • Understand the definition of buffering
  • Explore the primary causes of slow buffering
  • Learn methods for improving buffering speed

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What does buffering mean?

Buffering is the practice of pre-loading segments of data when streaming video content. Streaming — the continuous transmission of audio or video files from a server to a client — is the process that makes watching videos online possible. Buffering helps make streaming run more smoothly because videos can start playing before the entire video is loaded. Thanks to the buffering process, pre-loaded content will also continue to stream even when a connection is briefly interrupted.

Buffered content loaded in video player

Buffering is a core component of the streaming process. However, many viewers do not realize this and are only aware of the buffering process when it happens slowly or interrupts streaming. This is why viewers may use the word "buffering" to describe delays in content loading.

Buffering can be compared to a grocery store's inventory and shelving process. Stores maintain inventory so they can easily restock shelves and avoid inconveniencing customers. Grocery store customers generally go about their shopping without thinking about the stocking process unless an item they want is unavailable. In the same way, video players pre-load video segments to avoid disrupting the viewing experience.

What is a video segment?

All streaming video is divided into small segments or video frames that are a few seconds in length. This way, the entire video file does not need to be transmitted from the server to the client at once, and streaming can begin with only part of the video loaded. As the video begins playing, the rest of the segments are loaded and play once they are ready.

Why does buffering sometimes take a long time?

Buffering can happen slowly for many reasons. Generally, these issues are either on the user side or the network side, the latter meaning the Internet service provider (ISP) or streaming platform.

User-level issues

  • WiFi bandwidth: A WiFi connection is a type of local network. Every network has a bandwidth limit, or a maximum amount of data that can pass through at once. If a network is approaching its maximum bandwidth, the content will buffer slowly. For example, if five people are trying to stream five different videos on the same WiFi network on a Friday night, their videos may buffer slowly.
  • Slow Internet: Modem/router issues or weak WiFi signals can also slow down an Internet connection, reducing buffering speed. For example, the distance between a device and router can weaken a wireless connection. An old or damaged router may produce a weak WiFi signal, slowing Internet performance.
  • Device or client issues: Even with high-performing Internet, buffering can take place slowly on older devices that may not be able to keep up with today’s Internet speed standards. Additionally, browsers vary in their capacity to stream content, so browser choice may also contribute to slow buffering.
  • HD content: Streaming high-definition (HD) video content can also test a WiFi network’s bandwidth limits. HD videos contain more data per frame than standard definition (SD) videos. More data per frame means that devices must download larger video segments with more data packets, making slow buffering more likely.

Network-level issues

  • ISP issues: Just like a local WiFi network can experience congestion issues or other failures, so can ISPs. If an ISP is experiencing an outage or service interruptions, its customers will not be able to download data smoothly, and the content will buffer slowly — if it plays at all.
  • Streaming provider issues
    • Network strain: If too many people are requesting content worldwide, it can strain a streaming provider's network. If the streaming provider is overloaded, it will delay fulfilling those requests.
    • Latency: The time between user action and the application's response, or latency, is a common issue for streaming providers. Latency is often caused by server distance. If the streaming provider's servers are too far from a user, it will take longer for data packets to travel to the user and for the content to load.
    • TCP connection: The Transmission Control Protocol (TCP) works in conjunction with the Internet Protocol (IP) to maintain the connection between a server and a client and ensure data packets are delivered in order. A break in a TCP connection could prevent the client from receiving content from the server, causing slow buffering or preventing content playback altogether.

How to improve buffering speed

There are many different ways to improve buffering speed. However, the recommended approach will depend on the issue’s primary cause.

User-level issues

  • WiFi bandwidth: If limited bandwidth is causing slow buffering, users can restrict Internet use or upgrade their Internet package.
  • Slow Internet: An Ethernet cable physically connects devices to routers, which often improves Internet speed and reliability for a device.
  • Device or client issues: If using an older computer, try closing some tabs or using a newer device. Alternatively, streaming the content in a different browser could make a difference.

Network-level issues

Users are not able to fix an ISP's or streaming provider's outage or service interruption, but it is worth tracking their service status for diagnosing whether or not the problem is on their side. Most ISP and streaming providers maintain a service update webpage or social media account with regular status updates.

How can streaming providers improve buffering speed for customers?

Streaming providers play a critical role in ensuring that buffering does not happen slowly. For example, streaming providers can optimize their video content by selecting the proper encoding format for their needs. Video encoding involves compressing and converting video content into a form that is compatible with various platforms. The compression process reduces file size, facilitating smooth playback.

Streaming providers should also use a video content delivery network (CDN) solution like Cloudflare Stream. A CDN is a group of servers that copy and store (or cache) content to deliver it to end users. Video CDNs are designed to support video content. Using a video CDN reduces latency and speeds up the buffering process so that viewers can stream content without interruption.