Web Performance and the Impact of SPDY, HTTP/2 & QUIC - Part 5

Jean Tunis

This blog is the final installment in a 5-part series on APMdigest where I discuss web application performance and how new protocols like SPDY, HTTP/2, and QUIC will hopefully improve it so we can have happy website users.

Start with Web Performance 101: The Bandwidth Myth

Start with Web Performance 101: 4 Recommendations to Improve Web Performance

Start with Web Performance and the Impact of SPDY, HTTP/2 & QUIC - Part 1

Start with Web Performance and the Impact of SPDY, HTTP/2 & QUIC - Part 2

Start with Web Performance and the Impact of SPDY, HTTP/2 & QUIC - Part 3

Start with Web Performance and the Impact of SPDY, HTTP/2 & QUIC - Part 4

HTTP/2 Implementations

It has been almost a year since HTTP/2 has been a ratified standard. I talked about how widely support it is - only 4% of the top 2 million Alexa sites truly support it.

Does your website support it? What about your web host provider?

One place to check is the Google Chrome browser itself by going to Chrome Web Tools.


You can also check by doing a packet capture with Wireshark. Or go to tools.keycdn.com/http2-test.

By now, most web browsers support the new version of HTTP. The top five, Chrome, Firefox, IE/Edge, Opera and Safari all support HTTP/2, at least partially. The top two widely used web servers, Apache and Nginx, support it as well.

Previously, I mentioned a number of workarounds that developers used to make their websites faster with HTTP/1.1. Now with HTTP/2, some of these workarounds can actually degrade performance with HTTP/2 implementation.

The Unsharding

With only one connection per host that is allowed with HTTP/2, domain sharding can hurt a developer's attempt to improve performance. So if there was used previously, an upgrade to HTTP/2 means that the domains must be unsharded.

The Uncombine

Combining Javascript and CSS files into one file helped to reduce the amount of connections on HTTP/1.1. This is no longer needed with only one connection.

However, care must be taken with this. Doing this must be tested on a case-by-case basis. Some large files are able to compress better than smaller files. So it may not be to your advantage to uncombine the files if you have a lot of smaller files.

The Uninlining

Inlining scripts directly into the HTML was another way to reduce the number of connections and round-trips to the server. With HTTP/2, this is no longer needed with only one TCP connection.

HTTP/2 Pros & Cons

There are number of advantages of using HTTP/2, including:

■ Substantially and measurably improve end-user perceived latency over HTTP/1.1 using TCP

■ Address the head of line blocking problem in HTTP

■ Not require multiple connections to a server to enable parallelism, thus improving its use of TCP

■ Retain the semantics of HTTP/1.1, like header fields, status codes, etc.

■ Clearly define how HTTP/2.0 interacts with HTTP/1.x via new Upgrade header field

But, despite these advantages, there are still some disadvantages that the new protocol version has not addressed.

Some disadvantages are:

■ Unable to get around TCP head of line blocking, particularly during packet loss

■ TCP's congestion avoidance algorithm increases serialization delay

■ TLS connection setup still takes time

■ Binary format (for people like me) makes troubleshooting a bit more difficult, not being able to see plaintext, without TLS encryption keys

We Need to Be QUIC

So we see that we still have a number of limitations even with HTTP/2. Although, I have to admit, the last one is somewhat selfish.

One big limitation is the TCP protocol. Due to its connection-oriented nature, there's no getting around the head of line blocking and the time it takes to open and close the connection.

Google wanted a way around this, and in 2012 set out to develop a protocol that runs on top of UDP, which is connectionless protocol. The protocol is called Quick UDP Internet Connections, or QUIC. Another clever name by Google?

Clever or not, Google needed a protocol with quicker connection setup time and quicker retransmissions. Unlike TCP, UDP would allow for this. They wanted to take some of the benefits of the work done with SPDY, that ultimately went into the HTTP/2 standard, such as multiplexed HTTP communication, but running over UDP rather than TCP.

The main goal? To reduce overall latency across the Internet for a user's interactions.

QUIC implements various TCP features, but without the limitations, such as the round-trip time for connection setup, flow control, and congestion avoidance. With UDP's connectionless orientation, RTT is zero since UDP just starts sending data when it needs to rather than talking to the other side to ensure it's available to talk.

Where is QUIC?

The most common place I've come across QUIC being used is on YouTube.

Have you ever compared the speed of a YouTube video compared to some of the other providers like Wistia and Vimeo? Where I live, I'll be lucky to get 3Mbps from my ISP. Watching a video on YouTube rarely buffers. I can almost always count on buffering when watching a video hosted on Wistia or Vimeo. As you can see in the screenshot below, the protocol being used on YouTube is a mix of QUIC and SPDY.


Contrast that to the screenshot I took from Wistia's site, below.


They are still largely using HTTP/1.1. They're not even on HTTP/2 yet. I'm sure they are doing a number of other things to make their web properties faster, but that explains to me why I rarely get any buffering on YouTube compared to Wistia.

Conclusion

If the speed with which SPDY was tested and went into the HTTP/2 standard, which took about three years from SPDY draft release to HTTP/2 draft release, is it possible that we could have a replacement for the TCP protocol on the web in the next couple of years? This should be interesting and exciting!

Jean Tunis is Senior Consultant and Founder of RootPerformance.

Related Links

Hot Topics

The Latest

Observability Is the New Control Plane for Enterprise Transformation

The enterprises that will define the next decade are not the ones that deployed the most technology. They are the ones who understood what their technology was actually doing. That distinction is not a philosophical point. It is the central operational challenge facing every organization that has spent the last five years modernizing at speed ...

When AI Becomes the Corporate OS

AI is becoming the operating system of the enterprise. It acts as an invisible coordination layer that understands intent, connects systems, and executes work across complex SaaS environments. Previously, employees had to click through multiple systems — CRM, ERP, support tools, collaboration platforms — to complete a single task. Now, instead of navigating each application manually, they can simply state what they need to accomplish ...

The $600 Billion Wake Up Call

In 2026, the cost of downtime or an outage is no longer just a technical inconvenience; it's a $600 billion wake up call for global businesses. As our digital ecosystems become  more interconnected, each touchpoint introduces new risks and multiplies the consequences when things go wrong. And the data is clear: aggregate downtime costs  for Global 2,000 companies have surged 50% since 2024, reaching a staggering $600 billion ...

Breaking Down Agentic AI Fragmentation and Complexity with Governance

Deloitte found that 74% of enterprises expect to deploy agentic AI solutions in the next 24 months. However, the rush to deployment is outpacing foundational work, though. Only 21% of enterprises have fully formed agent governance models in place. The result? AI agents deployed without guidance or governance begin to function as fragmented islands of complexity ...

Cloud Spend Is Rising and Cloud Optimization Is Key to Funding AI and Protecting Margins

Cloud spending is no longer viewed as a passthrough IT expense, but as a strategic financial lever that directly impacts innovation capacity, profitability and enterprise resilience, according to the CFO Cloud Cost Optimization Report from Azul ...

Building AI Agents That Build Trust

As AI moves from generating responses to performing actions, the need for trust increases exponentially. And as organizations enlist AI agents for increasingly sophisticated business processes, trust is going to be the single most important theme for spurring adoption. What can organizations do to build trustworthy AI agents? ...

Keys to Building a Partner Ecosystem That Scales

I've spent a lot of time in the channel, and one thing I keep coming back to is this: a partner program is only as good as what it looks like in the field. Many programs look great on paper, but when a partner is in front of a customer navigating a complex hybrid environment or trying to make the case for AI-powered observability, the gap between what a vendor promises and what it actually delivers becomes very clear, very fast ...

How AI Agents Are Reshaping DataOps for the Always-On Enterprise

Enterprises today operate in a real-time environment where uninterrupted access to trusted data has become a baseline expectation for users, applications and automated systems. Traditional DataOps models, built on manual effort and human triage, cannot keep pace with this always active demand. AI agents are emerging as the operational backbone, ensuring consistent data availability, reinforcing trustworthiness and enabling a level of scale that manual processes cannot achieve ...

AI Deepfakes: Rethinking Trust in the Workplace

For decades, trust in the digital workplace rested on familiar signals. We trusted faces on video calls, voices on the phone, and emails that appeared to come from people we knew. These cues felt human and intuitive. They anchored how decisions were made, approvals were granted, and access was authorized. AI-powered deepfakes have quietly broken that model ...

Nine in Ten Enterprises Plan Cloud Data Repatriation amid Rising Cloud Costs and Data Sovereignty Mandates

Cloud migration was supposed to be a one-way door. For most enterprises, it turns out it isn't. Cloud data repatriation is a real and growing trend. A new survey ... finds that 89% of organizations plan to expand their on-premises infrastructure footprint over the next two years — and 75% have already moved at least some workloads back from public cloud in the past 24 months. The findings point to a broad rethinking of where data belongs ...

Web Performance and the Impact of SPDY, HTTP/2 & QUIC - Part 5

Jean Tunis

This blog is the final installment in a 5-part series on APMdigest where I discuss web application performance and how new protocols like SPDY, HTTP/2, and QUIC will hopefully improve it so we can have happy website users.

Start with Web Performance 101: The Bandwidth Myth

Start with Web Performance 101: 4 Recommendations to Improve Web Performance

Start with Web Performance and the Impact of SPDY, HTTP/2 & QUIC - Part 1

Start with Web Performance and the Impact of SPDY, HTTP/2 & QUIC - Part 2

Start with Web Performance and the Impact of SPDY, HTTP/2 & QUIC - Part 3

Start with Web Performance and the Impact of SPDY, HTTP/2 & QUIC - Part 4

HTTP/2 Implementations

It has been almost a year since HTTP/2 has been a ratified standard. I talked about how widely support it is - only 4% of the top 2 million Alexa sites truly support it.

Does your website support it? What about your web host provider?

One place to check is the Google Chrome browser itself by going to Chrome Web Tools.


You can also check by doing a packet capture with Wireshark. Or go to tools.keycdn.com/http2-test.

By now, most web browsers support the new version of HTTP. The top five, Chrome, Firefox, IE/Edge, Opera and Safari all support HTTP/2, at least partially. The top two widely used web servers, Apache and Nginx, support it as well.

Previously, I mentioned a number of workarounds that developers used to make their websites faster with HTTP/1.1. Now with HTTP/2, some of these workarounds can actually degrade performance with HTTP/2 implementation.

The Unsharding

With only one connection per host that is allowed with HTTP/2, domain sharding can hurt a developer's attempt to improve performance. So if there was used previously, an upgrade to HTTP/2 means that the domains must be unsharded.

The Uncombine

Combining Javascript and CSS files into one file helped to reduce the amount of connections on HTTP/1.1. This is no longer needed with only one connection.

However, care must be taken with this. Doing this must be tested on a case-by-case basis. Some large files are able to compress better than smaller files. So it may not be to your advantage to uncombine the files if you have a lot of smaller files.

The Uninlining

Inlining scripts directly into the HTML was another way to reduce the number of connections and round-trips to the server. With HTTP/2, this is no longer needed with only one TCP connection.

HTTP/2 Pros & Cons

There are number of advantages of using HTTP/2, including:

■ Substantially and measurably improve end-user perceived latency over HTTP/1.1 using TCP

■ Address the head of line blocking problem in HTTP

■ Not require multiple connections to a server to enable parallelism, thus improving its use of TCP

■ Retain the semantics of HTTP/1.1, like header fields, status codes, etc.

■ Clearly define how HTTP/2.0 interacts with HTTP/1.x via new Upgrade header field

But, despite these advantages, there are still some disadvantages that the new protocol version has not addressed.

Some disadvantages are:

■ Unable to get around TCP head of line blocking, particularly during packet loss

■ TCP's congestion avoidance algorithm increases serialization delay

■ TLS connection setup still takes time

■ Binary format (for people like me) makes troubleshooting a bit more difficult, not being able to see plaintext, without TLS encryption keys

We Need to Be QUIC

So we see that we still have a number of limitations even with HTTP/2. Although, I have to admit, the last one is somewhat selfish.

One big limitation is the TCP protocol. Due to its connection-oriented nature, there's no getting around the head of line blocking and the time it takes to open and close the connection.

Google wanted a way around this, and in 2012 set out to develop a protocol that runs on top of UDP, which is connectionless protocol. The protocol is called Quick UDP Internet Connections, or QUIC. Another clever name by Google?

Clever or not, Google needed a protocol with quicker connection setup time and quicker retransmissions. Unlike TCP, UDP would allow for this. They wanted to take some of the benefits of the work done with SPDY, that ultimately went into the HTTP/2 standard, such as multiplexed HTTP communication, but running over UDP rather than TCP.

The main goal? To reduce overall latency across the Internet for a user's interactions.

QUIC implements various TCP features, but without the limitations, such as the round-trip time for connection setup, flow control, and congestion avoidance. With UDP's connectionless orientation, RTT is zero since UDP just starts sending data when it needs to rather than talking to the other side to ensure it's available to talk.

Where is QUIC?

The most common place I've come across QUIC being used is on YouTube.

Have you ever compared the speed of a YouTube video compared to some of the other providers like Wistia and Vimeo? Where I live, I'll be lucky to get 3Mbps from my ISP. Watching a video on YouTube rarely buffers. I can almost always count on buffering when watching a video hosted on Wistia or Vimeo. As you can see in the screenshot below, the protocol being used on YouTube is a mix of QUIC and SPDY.


Contrast that to the screenshot I took from Wistia's site, below.


They are still largely using HTTP/1.1. They're not even on HTTP/2 yet. I'm sure they are doing a number of other things to make their web properties faster, but that explains to me why I rarely get any buffering on YouTube compared to Wistia.

Conclusion

If the speed with which SPDY was tested and went into the HTTP/2 standard, which took about three years from SPDY draft release to HTTP/2 draft release, is it possible that we could have a replacement for the TCP protocol on the web in the next couple of years? This should be interesting and exciting!

Jean Tunis is Senior Consultant and Founder of RootPerformance.

Related Links

Hot Topics

The Latest

Observability Is the New Control Plane for Enterprise Transformation

The enterprises that will define the next decade are not the ones that deployed the most technology. They are the ones who understood what their technology was actually doing. That distinction is not a philosophical point. It is the central operational challenge facing every organization that has spent the last five years modernizing at speed ...

When AI Becomes the Corporate OS

AI is becoming the operating system of the enterprise. It acts as an invisible coordination layer that understands intent, connects systems, and executes work across complex SaaS environments. Previously, employees had to click through multiple systems — CRM, ERP, support tools, collaboration platforms — to complete a single task. Now, instead of navigating each application manually, they can simply state what they need to accomplish ...

The $600 Billion Wake Up Call

In 2026, the cost of downtime or an outage is no longer just a technical inconvenience; it's a $600 billion wake up call for global businesses. As our digital ecosystems become  more interconnected, each touchpoint introduces new risks and multiplies the consequences when things go wrong. And the data is clear: aggregate downtime costs  for Global 2,000 companies have surged 50% since 2024, reaching a staggering $600 billion ...

Breaking Down Agentic AI Fragmentation and Complexity with Governance

Deloitte found that 74% of enterprises expect to deploy agentic AI solutions in the next 24 months. However, the rush to deployment is outpacing foundational work, though. Only 21% of enterprises have fully formed agent governance models in place. The result? AI agents deployed without guidance or governance begin to function as fragmented islands of complexity ...

Cloud Spend Is Rising and Cloud Optimization Is Key to Funding AI and Protecting Margins

Cloud spending is no longer viewed as a passthrough IT expense, but as a strategic financial lever that directly impacts innovation capacity, profitability and enterprise resilience, according to the CFO Cloud Cost Optimization Report from Azul ...

Building AI Agents That Build Trust

As AI moves from generating responses to performing actions, the need for trust increases exponentially. And as organizations enlist AI agents for increasingly sophisticated business processes, trust is going to be the single most important theme for spurring adoption. What can organizations do to build trustworthy AI agents? ...

Keys to Building a Partner Ecosystem That Scales

I've spent a lot of time in the channel, and one thing I keep coming back to is this: a partner program is only as good as what it looks like in the field. Many programs look great on paper, but when a partner is in front of a customer navigating a complex hybrid environment or trying to make the case for AI-powered observability, the gap between what a vendor promises and what it actually delivers becomes very clear, very fast ...

How AI Agents Are Reshaping DataOps for the Always-On Enterprise

Enterprises today operate in a real-time environment where uninterrupted access to trusted data has become a baseline expectation for users, applications and automated systems. Traditional DataOps models, built on manual effort and human triage, cannot keep pace with this always active demand. AI agents are emerging as the operational backbone, ensuring consistent data availability, reinforcing trustworthiness and enabling a level of scale that manual processes cannot achieve ...

AI Deepfakes: Rethinking Trust in the Workplace

For decades, trust in the digital workplace rested on familiar signals. We trusted faces on video calls, voices on the phone, and emails that appeared to come from people we knew. These cues felt human and intuitive. They anchored how decisions were made, approvals were granted, and access was authorized. AI-powered deepfakes have quietly broken that model ...

Nine in Ten Enterprises Plan Cloud Data Repatriation amid Rising Cloud Costs and Data Sovereignty Mandates

Cloud migration was supposed to be a one-way door. For most enterprises, it turns out it isn't. Cloud data repatriation is a real and growing trend. A new survey ... finds that 89% of organizations plan to expand their on-premises infrastructure footprint over the next two years — and 75% have already moved at least some workloads back from public cloud in the past 24 months. The findings point to a broad rethinking of where data belongs ...