What is web accelerator?

[更新: 2019年7月10日]

This page explains detailed specifications, creation methods, and usage methods for [Web Accelerator].

1. Overview

Web accelerator is a high-speed and low-cost web content distribution service used in Japan. When there is intensive access to a website, the display speed decreases or the server crashes. However, by installing web accelerator, it becomes possible to perform cache distribution. Also, the load caused by a rapid increase in access is distributed, and display on the website, etc. is stabilized.


Target Fee system Fees
Data transfer volume Usage-based fee JPY 5/1GiB (including tax)

*A free usage limit equivalent to 500GiB is available for each cloud account. At the web accelerator subordinate to the account, users can try up to 500GiB of data transfer for free. The free usage limit is only available once for each account. There is no expiration period for the free usage limit.
*Outbound traffic from the distribution system is subject to billing. (Inbound traffic is free.)

2. Basic specifications

Specifications for web accelerator provided by this service are listed below.

Support protocol HTTP, HTTPS (HTTP/2 support)
Installation location Domestic IDC
Distribution file No restrictions
Cache file size limit Restrictions exist (1GiB)
Restriction of number of sites Restrictions exist (20 sites)
Control panel Restrictions exist
API Restrictions exist (cache deletion)

Cache distribution

This service caches static contents at multiple web servers and disperses load before distribution.

Original domain, sub-domain

It is possible to use the original domain being used by the customer.
It is also possible to use a sub-domain (*) provided by SAKURA Internet.

*Random character string.user.webaccel.jp


Support is provided for encrypted communication using HTTPS.
Also, the HTTP/2 protocol is supported.

Cache deletion

Accessed contents are cached at a distribution server for a certain period of time. Therefore, even when the contents of the origin server are updated, old contents continue to remain cached for a certain period of time. If you want to clear the old cache, it is possible to forcibly clear the cache by using the cache deletion function.

Control panel

The web accelerator control panel provides functions such as a cache deletion function and a dashboard function for displaying graphs of traffic or requests.

Function Sub-functions Overview
Control panel Dashboard Function for confirming changes by using graphs of traffic and requests
Control panel Record of usage amount Function for confirming statistical information related to traffic and requests
Control panel Site list キャッシュ配信するサイトの一覧と、サイトの有効、無効を設定する機能
Control panel Cache deletion Function for deleting data that remain in the cache server

3. Detailed specifications

Service specifications

Function Use at the original domain Use at the sub-domain
HTTP distribution
HTTPS distribution
Access format Original domain (*) http(s)://random character string.user.webaccel.jp/

*CNAME records are a prerequisite for use at an original domain. Therefore, it is necessary to specify a host name such as www.example.com. Use is not possible at example.com. (based on RFC 1912 specifications)

Cache specifications

Initial settings Disable (*1)
Cache control Control at the Cache-Control: s-maxage response header of the origin server
Maximum cache retention period Maximum of 7 days
Maximum cachable
file size
1GiB per file (*2)

*1 For initial setting, caching is disabled. Therefore, please specify settings to enable caching.
*2 Files exceeding 1GiB are not cached and requests are issued to the origin server.


  • Please note that caching is not performed when settings have not been configured for s-maxage at the Cache-Control header.
  • For traffic that is not cached, please note that billing is applied to traffic that is distributed from web accelerator.
  • Settings for the cache time do not always guarantee that a cache is retained for the specified time. Caches may be deleted depending on access frequency and cache status.
  • There is the possibility that contents will be reacquired due to maintenance through the cache server. Please note that this does not always guarantee caching.
  • In order to prevent the caching of inappropriate contents (customer information such as the control panel, etc.), please be careful when configuring settings.

4. Preparation

Cache settings for contents at the origin server

*When configuring settings for cache time at the Cache-Control header, use s-maxage. For Apache, settings are configured as follows by using httpd.conf, .htaccess, etc.

Example) Settings when using 86400 seconds (1 day) cache for image files (extensions: .gif, .jpg, .jpeg, .png, .ico).

<Files ~ "\.(gif|jpe?g|png|ico)$">
  Header set Cache-Control "s-maxage=86400, public"

Opening of access port from cache server to origin server

The web accelerator cache server communication occurs from the following network to the origin server. At the origin server, configure settings to permit communication for HTTP (80)/HTTPS (443) from the networks listed below.

  • (added on January 31, 2017)


There may be an increase in client IP addresses due to facilities expansion.

5. Usage flow for each function

  • Usage procedures (original domain)
    • This method registers the FQDN generated by web accelerator as the CNAME record of the original domain.
      It is not necessary to modify web contents of the origin server.
  • Usage procedures (setting a new sub-domain in the original domain)
    • Although the same mechanism as the method listed above, this method is used by configuring settings for a new sub-domain in the existing domain.
      Although it is necessary to modify the web contents of the origin server, the preliminary test and reversion is made easier.
  • Original domain SSL function
    • These procedures are for when using the SSL function in an original domain.
      It is necessary to register the private key and certificate of the customer.
  • Usage procedures (sub-domain)
    • This method is used to convert the image file URL to FQDN generated by web accelerator.
      It is necessary to modify the web contents of the origin server.
  • Management functions
    • These are procedures for using management functions such as the record of usage amount, the dashboard function, the cache deletion function, etc.
  • Public API
    • These are procedures for using public API provided by web accelerator