How Fast Does a Website Need To Be?
By: Scott Barber
Abstract. Since at least the late 1990ís, many web development organizations have been asking the question ďWhat is the
industry standard response time for a web page?Ē As a result various attempts have been made to create such a standard, but
none of these standards have been generally accepted Ė largely because every web user has a different personal feeling about
whether a particular web page is responsive enough to be considered ďacceptableĒ. This paper demonstrates why a blanket
response time standard is not the best answer in terms of design criteria and explores the critical items that need to be considered
in determining appropriate response time goals for websites.
As an active member of the international Performance Testing community and as an experienced practitioner, I have seen
questions like this one posed numerous times:
"Iím desperately trying to find out what the industry standard response times are. What are reasonable benchmarks that
are acceptable for Web sites at the moment? Is 1.5 seconds a reasonable target????"
My answer to questions like this one always starts with "It depends on . . . " My friend Joe Strazzere addressed this
particular question quite well on a popular internet forum, as follows:
There are no industry standards. You must analyze your site in terms of who the customers are, what their needs are,
where they are located, what their equipment and connection speed might be, etc., etc. I suspect 1.5 seconds would be a
rather short interval for many situations. Do you really require that quick of a response?
The bottom line is that what seems fast is different in different situations. So how do you determine how fast is fast enough
for your application, and how do you convert that information into explicit, testable requirements? Those are the topics this
2. Considerations Affecting Performance Expectations
Letís start by discussing the leading factors that contribute to what we think fast is. I believe these considerations can be
divided into three broad categories:
ē user psychology
ē system considerations
ē usage considerations
None of these categories is any more or less important than the others. Whatís critical is to balance these considerations,
which weíll explore individually here, when determining performance requirements.
2.1. User Psychology
Of the three categories, user psychology is the one most often overlooked Ė or maybe a better way to say this is that user
psychology is often overridden by system and usage considerations. I submit that this is a mistake. User psychology plays
an important role in perceived performance, which is the most critical part of evaluating performance.
Consider this example. I recently filled out my tax return online. Itís a pretty simple process: you navigate through a Web
application that asks you questions to determine which pages are presented for you to enter data into. As I made a
preliminary pass through my return, I was happy with the performance (response time) of the application. When I later
went back to complete my return, I timed the page loads (because I almost always think about performance when I use the
Internet). Most of the pages returned in less than 5 seconds, but some of the section summary pages took almost a minute!
Why didnít I notice the first time through that some pages were this slow? Why didnít I get frustrated with this seemingly
poor performance? I usually notice performance as being poor at between 5 and 8 seconds, and at about 15 seconds Iíll
abandon a site or at least get frustrated. Thereís no science behind those numbers; theyíre just my personal tolerance levels.
So what made me wait a minute for some pages without even noticing that it was slow? The answer is that when I
requested a section summary page, an intermediate page came up that said:
"The information you have requested is being processed. This may take several minutes depending on the information you
have provided. Please be patient."
When I received that message, I went on to do something else for a minute. I went to get a drink, or checked one of my email
accounts, or any of a million other things, and when I came back the page was there waiting for me. I was satisfied. If
that message hadnít been presented and I had found myself just sitting and waiting for the page to display, I would have
become annoyed and eventually assumed that my request wasnít submitted properly, that the server had gone down, or
maybe that my Internet connection had been dropped.
So, getting back to the initial question of how fast is fast enough, from a user psychology perspective the answer is still "it
depends." It depends on several key factors that determine what is and isnít acceptable performance.
The first factor is the response time that users have become accustomed to based on previous experience. This is most
directly tied to the speed of their Internet connection. My mother, for example, has never experienced the Internet over
anything other than a fuzzy phone line with a 56.6-kilobytes-per-second modem. Iím used to surfing via high-speed
connections, so when I sign on at my motherís house Iím frustrated. My mother thinks Iím silly: "Scott, I think youíre
spoiled. Thatís as fast as we can get here, and a lot faster than we used to get! You never were very patient!" Sheís right Ė
Iím not very patient, so I have a low tolerance for poor Web site performance, whereas she has a high tolerance.
Another factor is activity type. All users understand that it takes time to download an MP3 or MPEG video, and therefore
have more tolerance if theyíre aware that thatís the activity theyíre performing. However, if users donít know that theyíre
performing an activity like downloading a file and are just waiting for the next page to load, theyíre likely to become
frustrated before they realize that the performance is actually acceptable for the activity theyíre performing.
This leads us to the factor of how user expectations have been set. If users know what to expect, as they do with the tax
preparation system I use, theyíre likely to be more tolerant of response times they might otherwise think of as slow. If you
tell users that the system will be fast and then it isnít, they wonít be happy. If you show users how fast it will be and then
follow through with that level of performance, theyíll generally be pretty happy.
The last factor we should discuss here is what I call surfing intent. When users want to accomplish a specific task, they
have less tolerance for poor performance than when theyíre casually looking for information or doing research. For
example, when I log on to the site I use to pay bills, I expect good performance. When Iím taking a break from work and
searching for the newest technology gadgets, I have a lot of tolerance for poor performance.
So with all of these variables you can see why, as Joe Strazzere said, "There are no industry standards." But if there are no
industry standards, how do we know where to start or what to compare against? Iíll describe some rules of thumb later,
when we get to the topic of collecting information about performance requirements.
2.2. System Considerations
System considerations are more commonly thought about than user psychology when weíre determining how fast is fast
enough. Stakeholders need to decide what kind of performance the system can handle within the given parameters. "Fastenough"
decisions are often based purely on the cost to achieve performance. While cost and feasibility are important, if
theyíre considered in a vacuum, youíll be doomed to fielding a system with poor performance.
Performance costs. The cost difference between building a system with "typical" performance and building a system with
"fast" performance is sometimes prohibitive. Only by balancing the need for performance against the cost can stakeholders
decide how much time and/or money theyíre willing to invest to improve performance.
System considerations include the following:
ē system hardware
ē network and/or Internet bandwidth of the system
ē geographical replication
ē software architecture
Entire books are dedicated to each of these considerations and many more. This is a well-documented and well-understood
aspect of performance engineering, so I wonít spend more time on it here.
2.3. Usage Considerations
Usage considerations are related to but separate from user psychology. The usage considerations Iím referring to have to do
with the way the Web site or Web application will be used. For example, is the application a shopping application? An
interactive financial planning application? A site containing current news? An internal human resources data entry
application? "Fast" means something different for each of these different applications. An application thatís used primarily
by employees to enter large volumes of data needs to be faster for users to be satisfied than a Web shopping site. A news
site can be fairly slow, as long as the text appears before the graphics. Interactive sites need to be faster than mostly static
sites. Sites that people use for work-related activities need to be faster than sites that are used primarily for recreational
These considerations are very specific to the site and the organization. There really isnít a lot of documentation available
about these types of considerations because theyíre so individual, depending on the specific application and associated user
base. Whatís important is to think about how your site will be used and to determine the performance tolerance of expected
users as compared to overall user psychology and system considerations. Iíll say more about this in the next section.
3. Collecting Information About Performance Requirements
So how do you translate the considerations described above into performance requirements? My approach is to first come
up with descriptions of explicit and implied performance requirements in these three areas:
ē user expectations
ē resource limitations
ē stakeholder expectations
In general, user and stakeholder expectations are complementary and donít require balancing between the two. For this
reason, I start by determining these requirements. Once Iíve done this, I try to balance those with the system/financial
resources that are available. Truth be told, I generally donít get to do the balancing. I usually collect the data and identify
the conflicts so that stakeholders can make decisions about how to balance expectations and resources to determine actual
Determining the actual requirements in the areas of speed, scalability, and stability and consolidating these into composite
requirements is the final step. Iíll describe that process in detail later on, but first letís look at each of the three areas where
youíll be collecting information about requirements.
3.1. User Expectations
A userís expectations when it comes to performance are all about end-to-end response time, as we touched on earlier in our
look at user psychology. Individual users donít know or care how many users can be on the system at a time, how the
system is designed to recover in case of disaster, or what the cost of building and maintaining the system has been.
When a new system is replacing an old one, itís critical from the userís perspective for the requirements of the new system
to be at least as stringent as the actual performance of the existing system. Users wonít be pleased with a new system if
their perception is that its performance is worse than the system itís replacing Ė regardless of whether the previous system
was a Web-based application, client/server, or some other configuration.
Aside from this situation, thereís no way to predict user expectations. Only users can tell you what they expect, so be sure
you take the time to poll users and find out what their expectations are before the requirements are set. Talk to users and
observe them using a similar type of system, maybe even a prototype of the system to be built. Remember that most users
donít think in terms of seconds, so to quantify their expectations youíll have to find a way to observe what they think is
fast, typical, or slow.
During my tenure as a performance engineer, Iíve done a lot of research in the area of user expectations. I believed at first
in the "8-second rule" that became popular in the mid-1990s, simply stating that most Web surfers consider 8 seconds to be
a reasonable download time for a page. But since then Iíve found no reliable research backing this rule of thumb, nor have
I found any correlation between this rule of thumb and actual user psychology. Iím going to share with you what I have
found, not to suggest these findings as standards but to give you a reasonable place to start as you poll your own users.
Iíve found that most users have the following expectations for normal page loads when surfing on high-speed connections:
ē no delay or fast Ė under 3 seconds
ē typical Ė 3 to 5 seconds
ē slow Ė 5 to 8 seconds
ē frustrating Ė 8 to 15 seconds
ē unacceptable Ė more than 15 seconds
In my experience, if your site is highly interactive or primarily used for data entry you should probably strive for page load
speeds about 20% faster than those listed. For mostly static or recreational sites, performance thatís about 25% slower than
the response times listed may still be acceptable.
For any kind of file download (MP3s, MPEGs, and such):
ē If the link for the file includes a file size and the download has a progress bar, users expect performance commensurate
with their connection speed.
ē If users are unaware theyíre downloading a file, the guidelines for normal pages apply.
For other activity:
ē Unless user expectations are set otherwise, the guidelines for normal pages apply.
ē If users are presented with a notice that this may take a while, theyíll wait significantly longer than without a notice, but
the actual amount of time theyíll wait varies drastically by individual.
When users are made aware of their connection speed, their expectations about performance shift accordingly. Part of my
experiments with users was to create pages with the response times in each of the categories above over a high-speed
connection, then to throttle back the connection speed and ask the users the same questions about performance. As long as I
told them the connection rate I was simulating, users rated the pages in the same categories, even though the actual
response times were very different.
One final note: Thereís a common industry perception that pages that users find "typical" or "slow" on high-speed
connections will be "frustrating" or "unacceptable" to users on slower connections. My research doesnít support this
theory. It does show that people who are used to high-speed connections at work but have slower dial-up connections at
home are often frustrated at home and try to do Internet tasks at work instead. But people who are used to slower
connections rate the same pages as fast, typical, slow, and unacceptable over their typical connection as people who are
used to high-speed connections and try to load these pages over their typical connection.
3.2. Resource Limitations
Limitations on resources such as time, money, people, hardware, networks, and software affect our performance
requirements, even though we really wish they didnít. For example, "You canít have any more hardware" is a resource
limitation, and whether we like it or not, it will likely contribute to determining our requirements.
Anecdotally, thereís a lot to say about the effects of resource limitations on performance requirements, but practically all it
really comes down to is this: Determine before you set your performance requirements what your available resources are,
so that when youíre setting the requirements, you can do so realistically.
3.3. Stakeholder Expectations
Unlike user expectations, stakeholder expectations are easy to obtain. Just ask any stakeholder what he or she expects.
"This system needs to be fast, it needs to support ten times the current user base, it needs to be up 100% of the time and
recover 100% of the data in case of down time, and it must be easy to use, make us lots of money, have hot coffee on my
desk when I arrive in the morning, and provide a cure for AIDS."
OK, thatís not something an actual stakeholder would say, but thatís what it feels like they often say when asked the
question. Itís our job to translate these lofty goals into something quantifiable and achievable, and thatís not always an easy
task. Usually stakeholders want "industry standards as written by market experts" to base their expectations on. As weíve
already discussed, there are no standards. In the absence of standards, stakeholders generally want systems so fast and
scalable that performance becomes a nonissue . . . until they find out how much that costs.
In short, stakeholders want the best possible system for the least possible money. This is as it should be. When it comes to
stakeholders, itís our job to help them determine, quantify, and manage system performance expectations. Of the three
determinants of performance requirements that weíve been discussing, the stakeholders have both the most information and
the most flexibility. User expectations very rarely change, and resource limitations are generally fairly static throughout a
performance testing/engineering effort. Stakeholder expectations, however, are likely to change when decisions have to be
made about tradeoffs.
Consider this. Recently Iíve been involved with several projects replacing client/server applications with Web-based
applications. In each case, the systems were primarily data entry systems. Initially, stakeholders wanted the performance of
the new application to match the performance of the previous client/server application. While this is in line with what I just
said about user expectations, itís not a reasonable expectation given system limitations. Web-based systems simply donít
perform that fast in general. And Iíve found that even users who are accustomed to a subsecond response time on a
client/server system are happy with a 3-second response time from a Web-based application. So Iíve had stakeholders sit
next to users on the prototypes (that were responding in 3 seconds or less) and had those users tell the stakeholders how
they felt about performance. When stakeholders realize that users are satisfied with a "3-second application," theyíre
willing to change the requirement to "under 3 seconds."
Speed, of course, isnít the only performance requirement. Stakeholders need to either inform you of what the other
requirements are or be the final authority for making decisions about those requirements. Itís our job to ensure that all of
the potential performance requirements are considered Ė eve
... to read more articles, visit http://sqa.fyicenter.com/art/