diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index da6a8808af..dba3520f1c 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -1332,3 +1332,34 @@ respdiff:sid:amd64:
     untracked: true
     expire_in: "1 day"
     when: on_failure
+
+# ABI check
+
+abi-check:sid:amd64:
+  <<: *debian_sid_amd64_image
+  stage: build
+  dependencies:
+    - autoreconf:sid:amd64
+  needs:
+    - autoreconf:sid:amd64
+  variables:
+    CC: gcc
+    CFLAGS: "${CFLAGS_COMMON} -Og"
+    BIND_BASELINE_VERSION: v9_16_0
+  script:
+    - *configure
+    - ${MAKE} -j${BUILD_PARALLEL_JOBS:-1} V=1
+    - git clone --branch "${BIND_BASELINE_VERSION}" --depth 1 https://gitlab.isc.org/isc-projects/bind9.git refbind
+    - cd refbind/
+    - *configure
+    - ${MAKE} -j${BUILD_PARALLEL_JOBS:-1} V=1
+    - cd ..
+    - util/api-checker.sh . refbind
+  artifacts:
+    paths:
+      - "*.html"
+      - "abi-*.dump"
+    expire_in: "1 week"
+  only:
+    - master@isc-projects/bind9
+    - /^v9_[1-9][0-9]$/@isc-projects/bind9
diff --git a/util/api-checker.sh b/util/api-checker.sh
new file mode 100755
index 0000000000..a424234eca
--- /dev/null
+++ b/util/api-checker.sh
@@ -0,0 +1,83 @@
+#!/bin/bash
+#
+# Copyright (C) Internet Systems Consortium, Inc. ("ISC")
+#
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+#
+# See the COPYRIGHT file distributed with this work for additional
+# information regarding copyright ownership.
+
+set -e
+
+# Exit if program $1 is not found in PATH.
+check_program() {
+	if ! command -v "${1}" > /dev/null 2>&1; then
+		echo "'${1}' not found in PATH" >&2
+		exit 1
+	fi
+}
+
+# Check that we were spawned with two arguments and that these arguments are two
+# different directories.
+check_args() {
+	if [ ${#} -ne 2 ] || [ ! -d "${1}" ] || [ ! -d "${2}" ] || [ "${1}" = "${2}" ]; then
+		echo "Usage:"
+		echo ""
+		echo "  ${0} <TESTDIR> <REFDIR>"
+		echo ""
+		echo "Generate API compatibility reports for BIND libraries."
+		echo ""
+		echo "  <TESTDIR> is a directory with current (new) BIND version"
+		echo "  <REFDIR> is a directory with reference (old) BIND version"
+		exit 1
+	fi
+}
+
+check_args "${@}"
+TESTBIND="${1}"
+REFBIND="${2}"
+
+# Ensure the required tools are available in PATH.
+check_program abi-dumper
+check_program abi-compliance-checker
+check_program git
+check_program w3m
+
+# Find all libraries which have designated 'api' file and
+# generate ABI dump file for them.
+while read -r SO; do
+	APIFILE="$(dirname "${SO}")/../api"
+	pushd "$(dirname "${APIFILE}")"
+	GIT_REVISION=$(git rev-parse HEAD | cut -c 1-10)
+	popd
+	# Get LIBINTERFACE, LIBREVISION, LIBAGE from the 'api' file.
+	eval "$(grep -v "^#" "${APIFILE}" | tr -d " ")"
+	VERSION="${LIBINTERFACE}.${LIBREVISION}.${LIBAGE}-${GIT_REVISION}"
+	abi-dumper "${SO}" -o abi-"$(basename "${SO}" .so)-${VERSION}".dump -lver "${VERSION}"
+done < <(find "${TESTBIND}"/lib/*/.libs/ "${REFBIND}"/lib/*/.libs/ -name '*.so')
+
+# Generate HTML API compatibility reports for all libraries.
+find . -maxdepth 1 -name 'abi-*.dump' | sort | while read -r OLD; read -r NEW; do
+	SONAME=${OLD/.\/abi-/}
+	SONAME=${SONAME/-*/}
+	if abi-compliance-checker -l "${SONAME}" -old "${OLD}" -new "${NEW}"; then
+		REPORT_PREFIX="PASS"
+	else
+		echo "***** Compatibility problems detected"
+		REPORT_PREFIX="WARN"
+	fi
+	OLD_REPORT_PATH="$(find "compat_reports/${SONAME}" -name '*.html')"
+	NEW_REPORT_PATH="${REPORT_PREFIX}-${SONAME}.html"
+	mv "${OLD_REPORT_PATH}" "${NEW_REPORT_PATH}"
+	echo
+done
+
+# Generate TXT API compatibility reports from HTML reports for all BIND libraries.
+echo "Generate TXT API compatibility reports from HTML reports for all BIND libraries:"
+while read -r HTMLREPORT; do
+	TXTREPORT="${HTMLREPORT/.html/.txt}"
+	echo "  w3m: ${HTMLREPORT} -> ${TXTREPORT}"
+	w3m -dump -cols 75 -O ascii -T text/html "${HTMLREPORT}" > "${TXTREPORT}"
+done < <(find . -maxdepth 1 -name '*.html')
diff --git a/util/copyrights b/util/copyrights
index 65f2e15d5a..8bc98fa185 100644
--- a/util/copyrights
+++ b/util/copyrights
@@ -2566,6 +2566,7 @@
 ./util/COPYRIGHT.NOM				X	2001,2004,2007,2016,2018,2019,2020
 ./util/COPYRIGHT.PORTION			X	1996,1997,1998,1999,2000,2001,2004,2007,2016,2018,2019,2020
 ./util/COPYRIGHT.TOP				X	2018,2019,2020
+./util/api-checker.sh				SH	2020
 ./util/bindkeys.pl				PERL	2009,2010,2011,2012,2014,2016,2017,2018,2019,2020
 ./util/branchsync.sh				SH	2013,2016,2018,2019,2020
 ./util/check-ans-prereq.sh			SH	2019,2020