Microsoft Corp. has once again improved its site speed and is now the fifth-fastest mobile site on the Internet Retailer Mobile Performance Index for the month of June.

The index monitored Internet Retailer’s Top 100 retailers’ mobile home pages from June 5-18, according to data provided by digital performance analytics company Catchpoint Systems Inc. Catchpoint provides Internet Retailer with two monthly site performance indexes: one for mobile sites and one for desktop sites.

Microsoft’s mobile site moved up 14 spots to No. 5 from No. 19 last month, as it loaded in 1.48 seconds during the two-week period in June compared with loading in 2.06 seconds on average during the two-week period in May, according to Catchpoint data.

The reason for the improved mobile site speed is because Microsoft reduced the size of the mobile site home page by 0.60 megabytes and is now only 0.67 megabytes to download, according to Catchpoint data. This is much lighter than the 100 retailers Catchpoint monitors, which had an average page weight of 2.24 megabytes for the June index.

On this month’s desktop performance index, Microsoft also was featured for its improved site speed, as it landed in the top 10 for desktop sites. The reason for its speedy desktop site was similar, as the retailer also reduced its desktop home-page weight.

Data provided by Catchpoint

“Both the mobile and desktop sites have improved performance and this is mainly due to the reduced number of items on the page, including scripts, images and hosts,” a Catchpoint spokesman says. Microsoft, No. 95 in the Internet Retailer 2017 Top 500, did not respond to a request for comment.

Catchpoint also notes that the three fastest mobile sites are the same in June as they were in May: Walgreen Co. (No. 39 in the Top 500), W.W. Grainger Inc. (No. 11) and Amazon.com Inc. (No. 1) ranked 1, 2 and 3, respectively.

“Walgreens in particular should be commended for being the only site on the index to deliver a sub-one second response time for the second month in a row,” a Catchpoint spokesman says. Walgreens.com loaded in 0.82 seconds on mobile devices on average between June 5-18.

For the two weeks of June 5-18, the Top 100 retailers’ average load time was 3.44 seconds compared with 3.34 seconds the previous month. The average page weight was 2.24 megabytes compared with 2.18 megabytes the previous month, and the average number of hosts was 47 compared with 46. The average number of items was 151 compared with 148 a month ago.

The 100 sites were, on average, 99.80% available June 5-18, compared with 99.89% available May 8-21. These are the 100 leading North American retail sites by online sales for 2015, according to Internet Retailer’s Top500Guide.com.

Catchpoint monitors each website’s home page with measurements taken from Catchpoint’s in-country or in-region monitoring nodes, at intervals of five minutes for two weeks each month. Backbone monitoring nodes are the locations of Catchpoint’s devices that are near data centers operated by the main internet service providers that provide service to a city. The nodes simulate end-user contact with each website. Catchpoint monitors webpage load time, availability, hosts and items.

They are defined as follows:

Web-page load time: The time it takes for enough page elements to load for a consumer to begin interacting with a page, such as searching, tapping or scrolling. From a consumer point of view, the time it takes for the progress bar or spinning wheel to stop.

Availability: The percentage of time during the two-week test week that the site can be successfully reached by a consumer.

Host: Any domain that delivers data, content or services over the internet to the site.

Items or Requests: Web page components, such as files or images that a page loads from internal and external hosts or domains. These can include PDFs, PNGs, JPEGs and GIFs.