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You can create a file /etc/pihole/pihole-FTL.conf that will be read by FTLDNS on startup.

Possible settings (the option shown first is the default):

DNS settings


How should FTL reply to blocked queries?
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CNAME_DEEP_INSPECT=true|false (PR #663)

Use this option to disable deep CNAME inspection. This might be beneficial for very low-end devices

BLOCK_ESNI=true|false (PR #733)

Encrypted Server Name Indication (ESNI) is certainly a good step into the right direction to enhance privacy on the web. It prevents on-path observers, including ISPs, coffee shop owners and firewalls, from intercepting the TLS Server Name Indication (SNI) extension by encrypting it. This prevents the SNI from being used to determine which websites users are visiting.

ESNI will obviously cause issues for pixelserv-tls which will be unable to generate matching certificates on-the-fly when it cannot read the SNI. Cloudflare and Firefox are already enabling ESNI. According to the IEFT draft (link above), we can easily restore piselserv-tls's operation by replying NXDOMAIN to _esni. subdomains of blocked domains as this mimics a "not configured for this domain" behavior.

EDNS0_ECS=true|false (PR #851)

Should we overwrite the query source when client information is provided through EDNS0 client subnet (ECS) information? This allows Pi-hole to obtain client IPs even if they are hidden behind the NAT of a router.

This feature has been requested and discussed on Discourse where further information how to use it can be found.

RATE_LIMIT=1000/60 (PR #1052)

Control FTL's query rate-limiting. Rate-limited queries are answered with a REFUSED reply and not further processed by FTL.

The default settings for FTL's rate-limiting are to permit no more than 1000 queries in 60 seconds. Both numbers can be customized independently. It is important to note that rate-limiting is happening on a per-client basis. Other clients can continue to use FTL while rate-limited clients are short-circuited at the same time.

For this setting, both numbers, the maximum number of queries within a given time, and the length of the time interval (seconds) have to be specified. For instance, if you want to set a rate limit of 1 query per hour, the option should look like RATE_LIMIT=1/3600.

Rate-limiting may be disabled altogether by setting RATE_LIMIT=0/0 (this results in the same behavior as before FTL v5.7).

REPLY_ADDR4 (no default, PR #965)

When using IP blocking mode, FTL determines the address of the interface a query arrived on. We then use this IP address in the blocked reply. This setting can be used to overwrite the replied IPv4 (A) address.

REPLY_ADDR6 (no default, PR #965)

When using IP blocking mode, FTL determines the address of the interface a query arrived on. We then use this IP address in the blocked reply. This setting can be used to overwrite the replied IPv6 (AAAA) address.


When the gravity database is locked/busy, how should Pi-hole handle queries?

  • ALLOW - allow all queries when the database is busy
  • BLOCK - block all queries when the database is busy. This uses the configured BLOCKINGMODE (default NULL)
  • REFUSE - refuse all queries which arrive while the database is busy
  • DROP - just drop the queries, i.e., never reply to them at all.

Despite REFUSE sounding similar to DROP, it turned out that many clients will just immediately retry, causing up to several thousands of queries per second. This does not happen in DROP mode.

Statistics settings


Up to how many hours of queries should be imported from the database and logs? Values greater than the hard-coded maximum of 24h need a locally compiled FTL with a changed compile-time value.


Which privacy level is used?
More details


Should FTL ignore queries coming from the local machine?


Should FTL analyze AAAA queries? The DNS server will handle AAAA queries the same way, reglardless of this setting. All this does is ignoring AAAA queries when computing the statistics of Pi-hole. This setting is considered obsolete and will be removed in a future version.


Should FTL only analyze A and AAAA queries?


Should FTL analyze and include automatically generated DNSSEC queries in the Query Log?

Other settings


Listen only for local socket connections or permit all connections


On which port should FTL be listening?


Should FTL try to resolve IPv6 addresses to hostnames?


Should FTL try to resolve IPv4 addresses to hostnames?


In certain configurations, you may want FTL to wait a given amount of time before trying to start the DNS revolver. This is typically found when network interfaces appear only late during system startup and the interface startup priorities are configured incorrectly. This setting takes any integer value between 0 and 300 seconds.

NICE=-10 (PR #798)

Can be used to change the niceness of Pi-hole FTL. Defaults to -10 and can be disabled altogether by setting a value of -999.

The nice value is an attribute that can be used to influence the CPU scheduler to favor or disfavor a process in scheduling decisions. The range of the nice value varies across UNIX systems. On modern Linux, the range is -20 (high priority = not very nice to other processes) to +19 (low priority).


IP addresses (and associated host names) older than the specified number of days are removed to avoid dead entries in the network overview table. This setting defaults to the same value as MAXDBDAYS above but can be changed independently if needed.

NAMES_FROM_NETDB=true|false (PR #784)

Control whether FTL should use the fallback option to try to obtain client names from checking the network table. This behavior can be disabled with this option

Assume an IPv6 client without a host names. However, the network table knows - though the client's MAC address - that this is the same device where we have a host name for another IP address (e.g., a DHCP server managed IPv4 address). In this case, we use the host name associated to the other address as this is the same device.


With this option, you can change how (and if) hourly PTR requests are made to check for changes in client and upstream server hostnames. The following options are available:

  • REFRESH_HOSTNAMES=IPV4 - Do the hourly PTR lookups only for IPv4 addresses This is the new default since Pi-hole FTL v5.3.2. It should resolve issues with more and more very short-lived PE IPv6 addresses coming up in a lot of networks.
  • REFRESH_HOSTNAMES=ALL - Do the hourly PTR lookups for all addresses This is the same as what we're doing with FTL v5.3(.1). This can create a lot of PTR queries for those with many IPv6 addresses in their networks.
  • REFRESH_HOSTNAMES=UNKNOWN - Only resolve unknown hostnames Already existing hostnames are never refreshedi, i.e., there will be no PTR queries made for clients where hostnames are known. This also means that known hostnames will not be updated once known.
  • REFRESH_HOSTNAMES=NONE - Don't do any hourly PTR lookups This means we look host names up exactly once (when we first see a client) and never again. You may miss future changes of host names.

PARSE_ARP_CACHE=true|false (PR #445)

This setting can be used to disable ARP cache processing. When disabled, client identification and the network table will stop working reliably.

Long-term database settings

Further details concerning the database


Should FTL load information from the database on startup to be aware of the most recent history?


How long should queries be stored in the database? Setting this to 0 disables the database


How often do we store queries in FTL's database [minutes]?


Specify the path and filename of FTL's SQLite3 long-term database. Setting this to DBFILE= disables the database altogether

File options


The location of FTL's log file. If you want to move the log file to a different place, also consider this FAQ article.


The file which contains the PID of FTL's main process.


The file containing the port FTL's API is listening on.


The file containing the socket FTL's API is listening on.


The config file of Pi-hole containing, e.g., the current blocking status (do not change).


The database containing MAC -> Vendor information for the network table.


Specify path and filename of FTL's SQLite3 gravity database. This database contains all domains relevant for Pi-hole's DNS blocking

Debugging options


Enable all debug flags. If this is set to true, all other debug config options are ignored.


Print debugging information about database actions. This prints performed SQL statements as well as some general information such as the time it took to store the queries and how many have been saved to the database.


Prints a list of the detected interfaces on the startup of pihole-FTL. Also, prints whether these interfaces are IPv4 or IPv6 interfaces.


Print debugging information about received EDNS(0) data.


Print information about shared memory locks. Messages will be generated when waiting, obtaining, and releasing a lock.


Print extensive query information (domains, types, replies, etc.). This has always been part of the legacy debug mode of pihole-FTL.


Print flags of queries received by the DNS hooks. Only effective when DEBUG_QUERIES is enabled as well.


Print information about shared memory buffers. Messages are either about creating or enlarging shmem objects or string injections.


Print information about garbage collection (GC): What is to be removed, how many have been removed and how long did GC take.


Print information about ARP table processing: How long did parsing take, whether read MAC addresses are valid, and if the macvendor.db file exists.


Controls if FTLDNS should print extended details about regex matching into pihole-FTL.log.

More details

DEBUG_API=false|true {#debug_api data-toc-label='Telnet API'}

Print extra debugging information during telnet API calls. Currently only used to send extra information when getting all queries.


Print information about overTime memory operations, such as initializing or moving overTime slots.


Print information about status changes for individual queries. This can be useful to identify unexpected unknown queries.


Print information about capabilities granted to the pihole-FTL process. The current capabilities are printed on receipt of SIGHUP, i.e., the current set of capabilities can be queried without restarting pihole-FTL (by setting DEBUG_CAPS=true and thereafter sending killall -HUP pihole-FTL).


Print file and line causing a dnsmasq event into FTL's log files. This is handy to implement additional hooks missing from FTL.

DEBUG_VECTORS=false|true (PR #725)

FTL uses dynamically allocated vectors for various tasks. This config option enables extensive debugging information such as information about allocation, referencing, deletion, and appending.

DEBUG_RESOLVER=false|true (PR #728)

Extensive information about hostname resolution like which DNS servers are used in the first and second hostname resolving tries (only affecting internally generated PTR queries).

DEBUG_EDNS0=false|true (PR #851)

Verbose logging during EDNS(0) header analysis.

DEBUG_CLIENTS=false|true (PR #762)

Log various important client events such as change of interface (e.g., client switching from WiFi to wired or VPN connection), as well as extensive reporting about how clients were assigned to its groups.

DEBUG_ALIASCLIENTS=false|true (PR #880)

Log information related to alias-client processing.

DEBUG_EVENTS=false|true (PR #881)

Log information regarding FTL's embedded event handling queue.

DEBUG_HELPER=false|true (PR #914)

Log information about script helpers, e.g., due to dhcp-script.

DEBUG_EXTRA=false|true (PR #994)

Temporary flag that may print additional information. This debug flag is meant to be used whenever needed for temporary investigations. The logged content may change without further notice at any time.

Last update: September 11, 2021
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