What is Response Time Testing?

A tester measures an app or site performance by collecting various data during a load or stress test. However, every test starts with sending a request to an application. Once a request is sent, the tester calculates the app's response time by estimating how much time it takes to respond to the specific request. 

Let's understand response time with real-life examples −

Offline example

Let's assume you are standing at the checkout counter of a grocery store. The cashier takes three minutes to process the products. Now, if you have a lot of customers waiting in front of you, that means you will have to wait for a few minutes before reaching the checkout person.

So, in this case, the total response time will be the time it takes to process the products ( 3 minutes) plus the time you have to wait to reach the cashier.

Online Example

Let's say you are buying groceries from an online store. You add your products in the basket, click checkout, and entering your details to car details to complete the payment.

Now a request will be sent to your bank's server via the online grocery's site. The payment will be confirmed once your bank approves it. If your bank is handling many requests simultaneously, it might take some time for the request to process. 

The response time will be the amount of time taken after you click 'pay' after entering the card details and the time it takes for your bank servers to process your request.

How to measure response time?

Response time is measured using test tools that manipulate an application's transaction response time from start to end. After entering an application in the test tools, the test engineer hits the API, allowing the tools to fetch the relevant APIs.

The response time of an application may vary from one tool to another. There are various reasons contributing to the variation of response time among different tools −

Each tool includes different methods of calculating the metrics.

Variation in load can also affect the response of an API.

Some applications may take more time while loading or simulation to a specific tool. That can affect the response time as well.

Some tools also come with different architecture, which can cause variation in response time.

Process of measuring response time

For measuring response time, testers perform a business process featuring start-to-end transactions. It may include action/s to complete a business task such as login to an application and making a purchase.

As stated above, the response time will vary from tool to tool. In this case, it may differ due to the tool's calculating metrics, load simulation, and capture speed.

It may also happen due to increased user loads when extra items are added during the purchase. Again, when the test is conducted back to back, it may increase resource consumption, leading to increased response time.

Types of Response Metrics

Average Response Time

It refers to the average time it takes for a server for every round trip. It includes the loading time of JavaScript files, images, CSS, HTML, XML, etc. Developers can remove or modify by identifying, then removing, or modifying the slow components.

Peak Response Time

It allows the developers to find the components slowing down the system. For instance, a large database query can affect the loading time of a website or system. The peak response time aids in finding all the complex components within the system and handle them efficiently.

Error Rate

The error rate features a mathematic calculation that measures the problem requests against all requests in percentage. It takes all incorrect HTTP codes and timed out counts requests into account.

Three Important Response Time Values

0.1 second − Applications returning a response time within 0.1 seconds are considered ideal. It means the applications or systems are responding instantly without interruption.

1.0 Second − If applications or systems are responding within 1 second, then they are acceptable. It means users are less likely to experience any interruption. It may delay their experience but won't cause the system to break down.

10 Seconds − It is the maximum limit of acceptance. If systems get delayed beyond 10 seconds, users will probably leave the site or application. However, considering today's competition, the maximum acceptable response time is limited to 6 seconds. 

Ways to improve the server response time

There are many ways to reduce the server response time of a website or application

Choose better web hosting platforms

Businesses are advised to invest in a high-performance hosting platform offering uninterrupted server response time. Stay away from free web hosting or web hosting services providing inadequate support.

Use Content Delivery Network

A content delivery network or CDN is a line of distributed networks of proxy servers and data centers. Hosting servers far away from the target audience is more likely to slow down the load time. Therefore, businesses should decide on a server closer to their target audiences. 

Optimize the databases

Databases are likely to gather massive data as time passes, causing a lag in the server response. Optimizing databases regularly will keep these issues at bay. 

Update PHP

PHP sometimes can consume a server's vital resources by fulfilling unnecessary tasks. Businesses using PHP must update their PHP version regularly to avoid the latency rate.

Reduce coding size

The coding structure primarily determines the response rate of a website. CSS, JavaScript, and external files are something that can make or break a website speed. Try to minify the codes by distributing js and CSS files as per their size and necessity.


Response time testing is a crucial element of performance testing as it determines how long a user has to wait after requesting the application. If the response is slow, the user is not happy, and he/she will probably move over to another application. In this day and age of competition, the need for a faster and user-friendly application is the need for every business's hour.


1. What are some tools for response time testing?

While many response time testing tools are available in the market, tools like JMeter, Load Runner, and AEM are preferred mainly by developers worldwide.

2. What is Response Time?

Response time is the time an application server or API takes to respond to a user's request. It is affected by many factors such as network bandwidth, number/types of requests, the number of users, and average think time of the system.

The response time has a significant influence on the performance of an application. Therefore, developers use it to measure the performance of an API's transaction and queries.