The Atomile CDN platform allows you to customize caching rules for your website content on edge servers. You can configure cache duration and other cache strategies based on file types, request URLs, and other parameters to achieve your desired caching behavior. In addition, when your website is accelerated and delivered through the Atomile CDN platform, some default caching rules are applied automatically. If no custom rules are configured, content from your origin follows these default cache rules on the CDN servers.

The Atomile CDN platform uses different caching strategies and default cache durations depending on your origin server response headers and the characteristics of user requests.

Default Cache Rules Based on Response Headers or Request Headers

• If the origin response header contains no-cache directives, such as Cache-Control:no-store,no-cache,must-revalidate,post-check=0,pre-check=0 or Pragma:no-cache, the CDN servers do not cache the content by default.
• If the request includes an Authorization header and the origin response does not contain Cache-Control:public, the CDN servers do not cache the content by default.
• If the origin response header does not contain the no-cache directives described above, or if the request includes an Authorization header but the origin response contains Cache-Control:public, caching follows the platform’s default caching strategy and duration or your custom cache rules. Note that some specific file types may still be configured as non-cacheable on CDN servers.

Default Cache Durations for Specific Conditions

Request Scope/Type	File Types/Protocol	Default Cache Strategy/Duration
Keep Query String Requests	php, aspx, asp, jsp, do, dwr, cgi, fcgi, action, ashx, axd, json	No Cache
Keep Query String Requests	mp4, ts, f4v, f4vcrc7z, apk, wdf, cab, dhp, exe, flv, gz, ipa, iso, mpk, MPQ, pbcv, pxl, qnp, r00, rar, xy, xy2, zip, CAB	30 days
Keep Query String Requests	shtml, html, htm, js	12 hours
Keep Query String Requests	gif, swf, png, bmp	24 hours
Ignore Query String Requests	cgi	10 minutes
All Requests	mp3, wma	12-24 hours
All Requests	wmv	24 hours
All Requests	Other file types	24 hours

You can customize or override these default caching rules by following the steps in this guide.

How to Set Cache Rules

1. Log in to the Atomile Console and select the appropriate product.
2. Go to Configuration, locate the domain you want to configure, and click Edit Configuration at the top or the Edit button to the right of the domain.
3. On the configuration page, find Cache Rules under Cache Optimization, and click Add.
4. On the rule editing page, configure the following options as needed.

Effective Range

The Atomile CDN platform provides the following options for the scope of your custom cache rules:

Option	Description
All Requests	This rule applies to all requests for the associated domain.
Only Homepage	This rule applies only to requests for the root path, for example, http://domain/ or https://domain/.
Specified File Types	This rule applies to requests for specified file types. You can select from the predefined list or enter custom file types. Separate multiple file types with ;, for example, ace;aac.
Specified URI	You can define specific URIs for this cache rule and choose either Exact Matching or Ignore the Parameter Matching. Multiple URIs can be separated with line breaks. Exact Matching: The requested URI must exactly match the configured URI for this rule to apply. Ignore the Parameter Matching: If the request URI contains a query string, the query string is ignored and only the portion before the ? is matched against the configured URI. Do not include http:// or https:// in the input. Enter only the URI part. For example, for https://domain/browse/index.html, configure only /browse/index.html.
Specified Directory	This rule applies to all requests for specified directories. Each directory must begin and end with / and can include letters, numbers, and certain special characters, such as underscores (_), hyphens (-), percent signs (%), and dots (.). For example, /file/1%1/ applies to http://domain/file/1%1/ and all files under that directory. Please separate multiple directories with line breaks.
URL Regular Expression	You can directly enter a regular expression. It does not need to begin with /. The platform automatically prefixes the URL with ^https?://[^/]/. For example, .*.jpg$ indicates that requests for JPG files across all domains associated with this rule match this policy.

In addition to selecting the effective range from the options above, you can further refine the rule in Advanced Range Settings. These settings work together with the Effective Range using an AND relationship to determine the final scope of the cache rule.

The Advanced Range Settings include the following options:

Parameter	Description
UA or Exception UA	Supports regular expressions. Spaces and tab characters are converted to \s, for example, ^Mozilla/4.0$ to include or exclude requests with this User-Agent header. Multiple UAs can be configured at the same time, with one UA per line.
Exception URL (Regex)	This option allows you to exclude specific request URLs from the cache rule. The regular expression format is the same as in URL Regular Expression above.

Cache Behavior

For requests matching the configured Effective Range, you can customize the cache duration on CDN servers. Atomile currently supports three cache duration strategies, as described below:

Parameter	Description
Cache	Sets a fixed cache duration. If your website files are updated at a stable frequency, a fixed cache duration can improve CDN cache hit rates and reduce origin traffic.
Follow Origin Cache Rules	If your website files include cache-related headers such as Expires or Cache-Control, the CDN servers follow the cache duration specified by the origin. However, you still need to specify a cache duration here. If the origin response does not include cache duration headers for any reason, the CDN uses the duration configured here.
Do Not Cache	If your website files require real-time updates, configure Do Not Cache. Every user request to the CDN edge servers fetches the content from the origin and returns it to the user without caching it on the edge servers.

The currently supported time units for cache duration are seconds, minutes, hours, and days. The default unit is hours.

When you choose Cache or Follow Origin Cache Rules, you can also configure Advanced Settings to customize cache behavior based on origin response headers and client reload requests.

Parameter	Description
Ignore No-Cache Header From Origin	The default value is No. See the introduction at the beginning of this document for details. If you choose Yes, all no-cache-related directives in the origin response header, such as Cache-Control: no-cache, are ignored, and the current cache rule is applied directly.
Ignore Authorization Header	The default value is No. See the introduction at the beginning of this document for details. If you choose Yes, requests with an Authorization header can still follow the current cache rule even if the origin response does not contain Cache-Control: public.
Ignore Client Refresh	Defines how client reload requests are handled. You can choose to ignore client reload requests, meaning the cached file is returned directly from the CDN during the cache period, or convert the request to If-Modified-Since. In the latter case, if the last modified time of the cached file on the CDN edge server is later than the client’s Last-Modified time, the cached file is returned; otherwise, a 304 Not Modified response is returned.

Case-Insensitive Match

If you choose Yes, the configured Effective Range is matched without regard to letter case. Requests whose URLs differ only by case both match the rule. For example, if you configure http://domain/a.jpg with a cache duration of 1 hour, both http://domain/a.jpg and http://domain/A.jpg are cached for 1 hour on CDN edge servers.

If you choose No, case differences are not ignored, and only requests that exactly match the case specified in Effective Range apply to the rule.

The default value for this setting is Yes.

Priority

In the Priority field, you can specify the priority of this rule. The system matches rules based on the user request. If multiple rules apply, the rule with the higher priority is applied first.

In addition to clicking Add to enter the detailed configuration page, you can also use Quick Configuration next to Add for a simplified cache rule setup. In Quick Configuration, the effective range defaults to all requests. You can choose either Cache or Follow Origin Cache Rules for cache duration, but Advanced Settings are not available there. You can also directly select Do Not Cache and quickly set the priority of this simple rule.

After completing the configuration, click OK, and then click Next to submit your settings. To minimize potential disruption to your production environment, we strongly recommend performing a Pre-deploy test in a staging environment. This important step ensures that your configuration is correct before it goes live.

After you confirm that the settings are correct, click Deploy Now to apply them in the live environment. The configuration typically takes effect within 3 to 5 minutes. For more information about pre-deployment testing and validation, refer to Deploy the Configurations to Staging Environment for Validation.

Notes

• The cache rules configured in this guide take effect on CDN servers.
• Different CDN solutions, such as Content Acceleration and Media Acceleration Live Broadcast, may apply different default cache rules to the same file types.
• The default rules listed here are for general reference only. If the default cache rules are critical for your website, contact Atomile technical support for confirmation.