diff --git a/.circleci/config.yml b/.circleci/config.yml
index 007b5fb2..075baf29 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -60,6 +60,7 @@ jobs:
       - run:
           name: install requirements
           command: |
+            pip install --upgrade pip
             pip install -r test-requirements.txt;
             pip install -r test-filesource-optional-requirements.txt;
             pip install -r consul-requirements.txt;
diff --git a/.ldrelease/config.yml b/.ldrelease/config.yml
index 9021210c..cc14b358 100644
--- a/.ldrelease/config.yml
+++ b/.ldrelease/config.yml
@@ -12,7 +12,8 @@ publications:
 
 branches:
   - name: main
-    description: 7.x
+    description: 8.x
+  - name: 7.x
   - name: 6.x
 
 jobs:
diff --git a/contract-tests/client_entity.py b/contract-tests/client_entity.py
index 5d2d5220..e835e4f4 100644
--- a/contract-tests/client_entity.py
+++ b/contract-tests/client_entity.py
@@ -12,6 +12,13 @@ def __init__(self, tag, config):
         self.log = logging.getLogger(tag)
         opts = {"sdk_key": config["credential"]}
 
+        tags = config.get('tags', {})
+        if tags:
+            opts['application'] = {
+                'id': tags.get('applicationId', ''),
+                'version': tags.get('applicationVersion', ''),
+            }
+
         if config.get("streaming") is not None:
             streaming = config["streaming"]
             if streaming.get("baseUri") is not None:
diff --git a/contract-tests/service.py b/contract-tests/service.py
index d9f8e0a5..79b0e621 100644
--- a/contract-tests/service.py
+++ b/contract-tests/service.py
@@ -63,6 +63,7 @@ def status():
             'all-flags-with-reasons',
             'all-flags-client-side-only',
             'all-flags-details-only-for-tracked-flags',
+            'tags',
         ]
     }
     return (json.dumps(body), 200, {'Content-type': 'application/json'})
diff --git a/ldclient/config.py b/ldclient/config.py
index dfe1a29a..faf6fcc1 100644
--- a/ldclient/config.py
+++ b/ldclient/config.py
@@ -7,7 +7,7 @@
 from typing import Optional, Callable, List, Any, Set
 
 from ldclient.feature_store import InMemoryFeatureStore
-from ldclient.util import log
+from ldclient.util import log, validate_application_info
 from ldclient.interfaces import BigSegmentStore, EventProcessor, FeatureStore, UpdateProcessor, FeatureRequester
 
 GET_LATEST_FEATURES_PATH = '/sdk/latest-flags'
@@ -173,7 +173,8 @@ def __init__(self,
                  wrapper_name: Optional[str]=None,
                  wrapper_version: Optional[str]=None,
                  http: HTTPConfig=HTTPConfig(),
-                 big_segments: Optional[BigSegmentsConfig]=None):
+                 big_segments: Optional[BigSegmentsConfig]=None,
+                 application: Optional[dict]=None):
         """
         :param sdk_key: The SDK key for your LaunchDarkly account. This is always required.
         :param base_uri: The base URL for the LaunchDarkly server. Most users should use the default
@@ -239,6 +240,7 @@ def __init__(self,
           servers.
         :param http: Optional properties for customizing the client's HTTP/HTTPS behavior. See
           :class:`HTTPConfig`.
+        :param application: Optional properties for setting application metadata. See :py:attr:`~application`
         """
         self.__sdk_key = sdk_key
 
@@ -271,6 +273,7 @@ def __init__(self,
         self.__wrapper_version = wrapper_version
         self.__http = http
         self.__big_segments = BigSegmentsConfig() if not big_segments else big_segments
+        self.__application = validate_application_info(application or {}, log)
 
     def copy_with_new_sdk_key(self, new_sdk_key: str) -> 'Config':
         """Returns a new ``Config`` instance that is the same as this one, except for having a different SDK key.
@@ -441,3 +444,16 @@ def big_segments(self) -> BigSegmentsConfig:
     def _validate(self):
         if self.offline is False and self.sdk_key is None or self.sdk_key == '':
             log.warning("Missing or blank sdk_key.")
+
+    @property
+    def application(self) -> dict:
+        """
+        An object that allows configuration of application metadata.
+
+        Application metadata may be used in LaunchDarkly analytics or other
+        product features, but does not affect feature flag evaluations.
+
+        If you want to set non-default values for any of these fields, provide
+        the appropriately configured dict to the {Config} object.
+        """
+        return self.__application
diff --git a/ldclient/impl/big_segments.py b/ldclient/impl/big_segments.py
index b6a013d3..bcd6e2b8 100644
--- a/ldclient/impl/big_segments.py
+++ b/ldclient/impl/big_segments.py
@@ -81,7 +81,6 @@ def get_user_membership(self, user_key: str) -> Tuple[Optional[dict], str]:
         membership = self.__cache.get(user_key)
         if membership is None:
             user_hash = _hash_for_user_key(user_key)
-            log.warn("*** querying Big Segments for user hash: %s" % user_hash)
             try:
                 membership = self.__store.get_membership(user_hash)
                 if membership is None:
diff --git a/ldclient/impl/http.py b/ldclient/impl/http.py
index ef36c8ba..858fd371 100644
--- a/ldclient/impl/http.py
+++ b/ldclient/impl/http.py
@@ -3,14 +3,34 @@
 from os import environ
 import urllib3
 
+def _application_header_value(application: dict) -> str:
+    parts = []
+    id = application.get('id', '')
+    version = application.get('version', '')
+
+    if id:
+        parts.append("application-id/%s" % id)
+
+    if version:
+        parts.append("application-version/%s" % version)
+
+    return " ".join(parts)
+
+
 def _base_headers(config):
     headers = {'Authorization': config.sdk_key or '',
                'User-Agent': 'PythonClient/' + VERSION}
+
+    app_value = _application_header_value(config.application)
+    if app_value:
+        headers['X-LaunchDarkly-Tags'] = app_value
+
     if isinstance(config.wrapper_name, str) and config.wrapper_name != "":
         wrapper_version = ""
         if isinstance(config.wrapper_version, str) and config.wrapper_version != "":
             wrapper_version = "/" + config.wrapper_version
         headers.update({'X-LaunchDarkly-Wrapper': config.wrapper_name + wrapper_version})
+
     return headers
 
 def _http_factory(config):
diff --git a/ldclient/util.py b/ldclient/util.py
index 66c0c70b..042f33dc 100644
--- a/ldclient/util.py
+++ b/ldclient/util.py
@@ -4,10 +4,12 @@
 # currently excluded from documentation - see docs/README.md
 
 import logging
+import re
 from os import environ
 import sys
 import urllib3
 
+from typing import Any
 from ldclient.impl.http import HTTPFactory, _base_headers
 
 log = logging.getLogger(sys.modules[__name__].__name__)
@@ -25,6 +27,26 @@
 
 _retryable_statuses = [400, 408, 429]
 
+def validate_application_info(application: dict, logger: logging.Logger) -> dict:
+    return {
+        "id": validate_application_value(application.get("id", ""), "id", logger),
+        "version": validate_application_value(application.get("version", ""), "version", logger),
+    }
+
+def validate_application_value(value: Any, name: str, logger: logging.Logger) -> str:
+    if not isinstance(value, str):
+        return ""
+
+    if len(value) > 64:
+        logger.warning('Value of application[%s] was longer than 64 characters and was discarded' % name)
+        return ""
+
+    if re.search(r"[^a-zA-Z0-9._-]", value):
+        logger.warning('Value of application[%s] contained invalid characters and was discarded' % name)
+        return ""
+
+    return value
+
 def _headers(config):
     base_headers = _base_headers(config)
     base_headers.update({'Content-Type': "application/json"})
diff --git a/testing/test_config.py b/testing/test_config.py
index 701e70e5..7c5e342d 100644
--- a/testing/test_config.py
+++ b/testing/test_config.py
@@ -1,4 +1,5 @@
 from ldclient.config import Config
+import pytest
 
 
 def test_copy_config():
@@ -40,3 +41,29 @@ def test_trims_trailing_slashes_on_uris():
     assert config.base_uri == "https://launchdarkly.com"
     assert config.events_uri == "https://docs.launchdarkly.com/bulk"
     assert config.stream_base_uri == "https://blog.launchdarkly.com"
+
+def application_can_be_set_and_read():
+    application = {"id": "my-id", "version": "abcdef"}
+    config = Config(sdk_key = "SDK_KEY", application = application)
+    assert config.application == {"id": "my-id", "version": "abcdef"}
+
+def application_can_handle_non_string_values():
+    application = {"id": 1, "version": 2}
+    config = Config(sdk_key = "SDK_KEY", application = application)
+    assert config.application == {"id": "1", "version": "2"}
+
+def application_will_ignore_invalid_keys():
+    application = {"invalid": 1, "key": 2}
+    config = Config(sdk_key = "SDK_KEY", application = application)
+    assert config.application == {"id": "", "version": ""}
+
+@pytest.fixture(params = [
+    " ",
+    "@",
+    ":",
+    "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789._-a"
+])
+def application_will_drop_invalid_values(value):
+    application = {"id": value, "version": value}
+    config = Config(sdk_key = "SDK_KEY", application = application)
+    assert config.application == {"id": "", "version": ""}
diff --git a/testing/test_event_processor.py b/testing/test_event_processor.py
index 363d980e..ec777812 100644
--- a/testing/test_event_processor.py
+++ b/testing/test_event_processor.py
@@ -484,6 +484,22 @@ def test_wrapper_header_sent_without_version():
 
         assert mock_http.request_headers.get('X-LaunchDarkly-Wrapper') == "Flask"
 
+def test_application_header_not_sent_when_not_set():
+    with DefaultTestProcessor() as ep:
+        ep.send_event({ 'kind': 'identify', 'user': user })
+        ep.flush()
+        ep._wait_until_inactive()
+
+        assert mock_http.request_headers.get('X-LaunchDarkly-Tags') is None
+
+def test_application_header_sent_when_set():
+    with DefaultTestProcessor(wrapper_name = "Flask", application = {"id": "my-id", "version": "my-version"}) as ep:
+        ep.send_event({ 'kind': 'identify', 'user': user })
+        ep.flush()
+        ep._wait_until_inactive()
+
+        assert mock_http.request_headers.get('X-LaunchDarkly-Tags') == "application-id/my-id application-version/my-version"
+
 def test_event_schema_set_on_event_send():
     with DefaultTestProcessor() as ep:
         ep.send_event({ 'kind': 'identify', 'user': user })
diff --git a/testing/test_feature_requester.py b/testing/test_feature_requester.py
index db18f555..031167dc 100644
--- a/testing/test_feature_requester.py
+++ b/testing/test_feature_requester.py
@@ -35,6 +35,7 @@ def test_get_all_data_sends_headers():
         assert req.headers['Authorization'] == 'sdk-key'
         assert req.headers['User-Agent'] == 'PythonClient/' + VERSION
         assert req.headers.get('X-LaunchDarkly-Wrapper') is None
+        assert req.headers.get('X-LaunchDarkly-Tags') is None
 
 def test_get_all_data_sends_wrapper_header():
     with start_server() as server:
@@ -62,6 +63,19 @@ def test_get_all_data_sends_wrapper_header_without_version():
         req = server.require_request()
         assert req.headers.get('X-LaunchDarkly-Wrapper') == 'Flask'
 
+def test_get_all_data_sends_tags_header():
+    with start_server() as server:
+        config = Config(sdk_key = 'sdk-key', base_uri = server.uri,
+                application = {"id": "my-id", "version": "my-version"})
+        fr = FeatureRequesterImpl(config)
+
+        resp_data = { 'flags': {}, 'segments': {} }
+        server.for_path('/sdk/latest-all', JsonResponse(resp_data))
+
+        fr.get_all_data()
+        req = server.require_request()
+        assert req.headers.get('X-LaunchDarkly-Tags') == 'application-id/my-id application-version/my-version'
+
 def test_get_all_data_can_use_cached_data():
     with start_server() as server:
         config = Config(sdk_key = 'sdk-key', base_uri = server.uri)
diff --git a/testing/test_ldclient_end_to_end.py b/testing/test_ldclient_end_to_end.py
index 7003805a..3f550d0f 100644
--- a/testing/test_ldclient_end_to_end.py
+++ b/testing/test_ldclient_end_to_end.py
@@ -102,12 +102,12 @@ def test_client_sends_diagnostics():
                 data = json.loads(r.body)
                 assert data['kind'] == 'diagnostic-init'
 
-# The TLS tests are skipped in Python 3.3 because the embedded HTTPS server does not work correctly, causing
+# The TLS tests are skipped in Python 3.7 because the embedded HTTPS server does not work correctly, causing
 # a TLS handshake failure on the client side. It's unclear whether this is a problem with the self-signed
 # certificate we are using or with some other server settings, but it does not appear to be a client-side
-# problem.
+# problem since we know that the SDK is able to connect to secure LD endpoints.
 
-@pytest.mark.skipif(sys.version_info.major == 3 and sys.version_info.minor == 3, reason = "test is skipped in Python 3.3")
+@pytest.mark.skipif(sys.version_info.major == 3 and sys.version_info.minor == 7, reason = "test is skipped in Python 3.7")
 def test_cannot_connect_with_selfsigned_cert_by_default():
     with start_secure_server() as server:
         server.for_path('/sdk/latest-all', poll_content())
@@ -120,7 +120,7 @@ def test_cannot_connect_with_selfsigned_cert_by_default():
         with LDClient(config = config, start_wait = 1.5) as client:
             assert not client.is_initialized()
 
-@pytest.mark.skipif(sys.version_info.major == 3 and sys.version_info.minor == 3, reason = "test is skipped in Python 3.3")
+@pytest.mark.skipif(sys.version_info.major == 3 and sys.version_info.minor == 7, reason = "test is skipped in Python 3.7")
 def test_can_connect_with_selfsigned_cert_if_ssl_verify_is_false():
     with start_secure_server() as server:
         server.for_path('/sdk/latest-all', poll_content())
@@ -134,7 +134,7 @@ def test_can_connect_with_selfsigned_cert_if_ssl_verify_is_false():
         with LDClient(config = config) as client:
             assert client.is_initialized()
 
-@pytest.mark.skipif(sys.version_info.major == 3 and sys.version_info.minor == 3, reason = "test is skipped in Python 3.3")
+@pytest.mark.skipif(sys.version_info.major == 3 and sys.version_info.minor == 7, reason = "test is skipped in Python 3.7")
 def test_can_connect_with_selfsigned_cert_if_disable_ssl_verification_is_true():
     with start_secure_server() as server:
         server.for_path('/sdk/latest-all', poll_content())
@@ -148,7 +148,7 @@ def test_can_connect_with_selfsigned_cert_if_disable_ssl_verification_is_true():
         with LDClient(config = config) as client:
             assert client.is_initialized()
 
-@pytest.mark.skipif(sys.version_info.major == 3 and sys.version_info.minor == 3, reason = "test is skipped in Python 3.3")
+@pytest.mark.skipif(sys.version_info.major == 3 and sys.version_info.minor == 7, reason = "test is skipped in Python 3.7")
 def test_can_connect_with_selfsigned_cert_by_setting_ca_certs():
     with start_secure_server() as server:
         server.for_path('/sdk/latest-all', poll_content())
diff --git a/testing/test_streaming.py b/testing/test_streaming.py
index 1838e500..82700b4d 100644
--- a/testing/test_streaming.py
+++ b/testing/test_streaming.py
@@ -38,6 +38,7 @@ def test_request_properties():
                 assert req.headers.get('Authorization') == 'sdk-key'
                 assert req.headers.get('User-Agent') == 'PythonClient/' + VERSION
                 assert req.headers.get('X-LaunchDarkly-Wrapper') is None
+                assert req.headers.get('X-LaunchDarkly-Tags') is None
 
 def test_sends_wrapper_header():
     store = InMemoryFeatureStore()
@@ -69,6 +70,21 @@ def test_sends_wrapper_header_without_version():
                 req = server.await_request()
                 assert req.headers.get('X-LaunchDarkly-Wrapper') == 'Flask'
 
+def test_sends_tag_header():
+    store = InMemoryFeatureStore()
+    ready = Event()
+
+    with start_server() as server:
+        with stream_content(make_put_event()) as stream:
+            config = Config(sdk_key = 'sdk-key', stream_uri = server.uri,
+                            application = {"id": "my-id", "version": "my-version"})
+            server.for_path('/all', stream)
+
+            with StreamingUpdateProcessor(config, store, ready, None) as sp:
+                sp.start()
+                req = server.await_request()
+                assert req.headers.get('X-LaunchDarkly-Tags') == 'application-id/my-id application-version/my-version'
+
 def test_receives_put_event():
     store = InMemoryFeatureStore()
     ready = Event()