searxng/docs/dev/engines/engine_overview.rst

Engine Overview

Further reading ..

• configured engines
• settings engine

SearXNG is a metasearch-engine, so it uses different search engines to provide better results.

Because there is no general search API which could be used for every search engine, an adapter has to be built between SearXNG and the external search engines. Adapters are stored under the folder searx/engines.

General Engine Configuration

It is required to tell SearXNG the type of results the engine provides. The arguments can be set in the engine file or in the settings file (normally settings.yml). The arguments in the settings file override the ones in the engine file.

It does not matter if an option is stored in the engine file or in the settings. However, the standard way is the following:

Engine File

Common options in the engine module

argument	type	information
categories	list	categories, in which the engine is working
paging	boolean	support multiple pages
time_range_support	boolean	support search time range
engine_type	str	online [ref] <online engines> by default, other possibles values are: offline [ref] <offline engines> online_dictionary [ref] <online dictionary> online_currency [ref] <online currency> online_url_search [ref] <online url search>

Engine settings.yml

For a more detailed description, see settings engine in the settings.yml.

Common options in the engine setup (settings.yml)

argument	type	information
name	string	name of search-engine
engine	string	name of searxng-engine (file name without .py)
enable_http	bool	enable HTTP (by default only HTTPS is enabled).
shortcut	string	shortcut of search-engine
timeout	string	specific timeout for search-engine
display_error_messages	boolean	display error messages on the web UI
proxies	dict	set proxies for a specific engine (e.g. proxies : {http: socks5://proxy:port, https: socks5://proxy:port})

Overrides

A few of the options have default values in the namespace of the engine's python module, but are often overwritten by the settings. If None is assigned to an option in the engine file, it has to be redefined in the settings, otherwise SearXNG will not start with that engine (global names with a leading underline can be None).

Here is an very simple example of the global names in the namespace of engine's module:

# engine dependent config
categories = ['general']
paging = True
_non_overwritten_global = 'foo'

The naming of overrides is arbitrary / recommended overrides are:

argument	type	information
base_url	string	base-url, can be overwritten to use same engine on other URL
number_of_results	int	maximum number of results per request
language	string	ISO code of language and country like en_US
api_key	string	api-key if required by engine

Making a Request

To perform a search an URL have to be specified. In addition to specifying an URL, arguments can be passed to the query.

Passed Arguments (request)

These arguments can be used to construct the search query. Furthermore, parameters with default value can be redefined for special purposes.

If the engine_type is :pyonline <searx.search.processors.online.OnlineProcessor.get_params>

argument	type	default-value, information
url	str	''
method	str	'GET'
headers	set	{}
data	set	{}
cookies	set	{}
verify	bool	True
headers.User-Agent	str	a random User-Agent
category	str	current category, like 'general'
safesearch	int	0, between 0 and 2 (normal, moderate, strict)
time_range	Optional[str]	None, can be day, week, month, year
pageno	int	current pagenumber
searxng_locale	str	SearXNG's locale selected by user. Specific language code like 'en', 'en-US', or 'all' if unspecified.

If the engine_type is :pyonline_dictionary <searx.search.processors.online_dictionary.OnlineDictionaryProcessor.get_params>, in addition to the online <engine request online> arguments:

argument	type	default-value, information
from_lang	str	specific language code like 'en_US'
to_lang	str	specific language code like 'en_US'
query	str	the text query without the languages

If the engine_type is :pyonline_currency <searx.search.processors.online_currency.OnlineCurrencyProcessor.get_params>, in addition to the online <engine request online> arguments:

argument	type	default-value, information
amount	float	the amount to convert
from	str	ISO 4217 code
to	str	ISO 4217 code
from_name	str	currency name
to_name	str	currency name

If the engine_type is :pyonline_url_search <searx.search.processors.online_url_search.OnlineUrlSearchProcessor.get_params>, in addition to the online <engine request online> arguments:

argument	type	default-value, information
search_url	dict	URLs from the search query: { 'http': str, 'ftp': str, 'data:image': str }

Specify Request

The function :pydef request(query, params): <searx.engines.demo_online.request> always returns the params variable, the following parameters can be used to specify a search request:

argument	type	information
url	str	requested url
method	str	HTTP request method
headers	set	HTTP header information
data	set	HTTP data information
cookies	set	HTTP cookies
verify	bool	Performing SSL-Validity check
allow_redirects	bool	Follow redirects
max_redirects	int	maximum redirects, hard limit
soft_max_redirects	int	maximum redirects, soft limit. Record an error but don't stop the engine
raise_for_httperror	bool	True by default: raise an exception if the HTTP code of response is >= 300

Making a Response

In the response function of the engine, the HTTP response (resp) is parsed and a list of results is returned.

A engine can append result-items of different media-types and different result-types to the result list. The list of the result items is render to HTML by templates. For more details read section:

• simple theme templates
• result types