diff --git a/deployment/community/.env.template b/deployment/community/.env.template
index 741e0e9c..ce910efd 100644
--- a/deployment/community/.env.template
+++ b/deployment/community/.env.template
@@ -208,3 +208,7 @@ GEVENT_WORKER=True
 # Deprecated from 2024.7.0, replacement is to set GEVENT_WORKER=True
 NO_MONKEY_PATCH=False
 
+# Diagnostic logs
+
+DIAGNOSTIC_LOGS_DIR=/diagnostic_logs
+
diff --git a/deployment/community/README.md b/deployment/community/README.md
index e99b90c3..9f6ab420 100644
--- a/deployment/community/README.md
+++ b/deployment/community/README.md
@@ -13,4 +13,6 @@ cp .env.template .prod.env
 
 Next step is to create data directory for mergin maps `projects` with proper permissions. Should you prefer a different location, please do search and replace it in config files (`.prod.env`, `docker-compose.yml`). Make sure your volume is large enough since mergin maps keeps all projects files, their history and also needs some space for temporary processing.
 
+If you want to persist diagnostic logs, create data directory `diagnostic_logs` with proper permissions.
+
 For more details about deployment please check [docs](https://merginmaps.com/docs/server/install/#deployment).
diff --git a/deployment/community/docker-compose.yml b/deployment/community/docker-compose.yml
index 9ee27549..8b5d5156 100644
--- a/deployment/community/docker-compose.yml
+++ b/deployment/community/docker-compose.yml
@@ -29,6 +29,7 @@ services:
     user: 901:999
     volumes:
       - ./projects:/data
+      - ./diagnostic_logs:/diagnostic_logs
       - ../common/entrypoint.sh:/app/entrypoint.sh
     env_file:
       - .prod.env
diff --git a/deployment/enterprise/.env.template b/deployment/enterprise/.env.template
index f6bda021..762bdd14 100644
--- a/deployment/enterprise/.env.template
+++ b/deployment/enterprise/.env.template
@@ -215,3 +215,6 @@ VECTOR_TILES_STYLE_URL=https://tiles-ee.merginmaps.com//styles/default.json
 #QGIS_EXTRACTOR_TIMEOUT=60
 
 #OVERVIEW_MAX_FILE_SIZE=1048576 # 1MB
+
+# Diagnostic logs from Mobile and QGIS Plugin
+DIAGNOSTIC_LOGS_DIR=/diagnostic_logs
diff --git a/deployment/enterprise/docker-compose.yml b/deployment/enterprise/docker-compose.yml
index cb5084c8..3bf085e4 100644
--- a/deployment/enterprise/docker-compose.yml
+++ b/deployment/enterprise/docker-compose.yml
@@ -12,6 +12,7 @@ services:
     command: ["gunicorn -w 4 --config config.py application:application"]
     volumes:
       - ./data:/data  # map data dir to host
+      - ./diagnostic_logs:/diagnostic_logs # diagnostic logs dir
       - ../common/entrypoint.sh:/app/entrypoint.sh
     env_file:
       - .prod.env
diff --git a/server/.test.env b/server/.test.env
index 908db5b9..bdaa7bfa 100644
--- a/server/.test.env
+++ b/server/.test.env
@@ -23,3 +23,4 @@ GEODIFF_WORKING_DIR=/tmp/geodiff
 SECURITY_BEARER_SALT='bearer'
 SECURITY_EMAIL_SALT='email'
 SECURITY_PASSWORD_SALT='password'
+DIAGNOSTIC_LOGS_DIR=/tmp/diagnostic_logs
diff --git a/server/application.py b/server/application.py
index 5cb08b69..b1ab79ac 100644
--- a/server/application.py
+++ b/server/application.py
@@ -46,6 +46,7 @@
         "GLOBAL_READ",
         "GLOBAL_WRITE",
         "ENABLE_SUPERADMIN_ASSIGNMENT",
+        "DIAGNOSTIC_LOGS_URL",
     ]
 )
 register_stats(application)
diff --git a/server/mergin/api.yaml b/server/mergin/api.yaml
new file mode 100644
index 00000000..6ebd2777
--- /dev/null
+++ b/server/mergin/api.yaml
@@ -0,0 +1,84 @@
+openapi: 3.0.0
+info:
+  description: Common Mergin Maps API
+  version: "0.1"
+  title: Common Mergin Maps API
+servers:
+  - url: /
+paths:
+  /v1/latest-version:
+    get:
+      summary: Fetch latest available server version
+      operationId: get_latest_version
+      responses:
+        "200":
+          description: Latest version info
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/ServerVersion"
+        "400":
+          $ref: "#/components/responses/BadRequestResp"
+        "404":
+          $ref: "#/components/responses/NotFoundResp"
+      x-openapi-router-controller: mergin.controller
+  /v2/diagnostic-logs:
+    post:
+      summary: Save diagnostic log to the server
+      description: This endpoint allows users to upload diagnostic logs for troubleshooting purposes from mobile and plugin.
+      operationId: save_diagnostic_log
+      x-openapi-router-controller: mergin.controller
+      parameters:
+        - name: app
+          in: query
+          description: Application name (e.g., "input-android-0.9.0")
+          required: true
+          schema:
+            type: string
+      requestBody:
+        required: true
+        content:
+          text/plain:
+            schema:
+              type: string
+              description: Log content in plain text
+      responses:
+        "200":
+          description: Log saved successfully
+        "400":
+          $ref: "#/components/responses/BadRequestResp"
+        "404":
+          $ref: "#/components/responses/NotFoundResp"
+        "413":
+          $ref: "#/components/responses/RequestTooLarge"
+components:
+  responses:
+    UnauthorizedError:
+      description: Authentication information is missing or invalid.
+    NotFoundResp:
+      description: Not found
+    BadRequestResp:
+      description: Invalid request.
+    RequestTooLarge:
+      description: Request Entity Too Large.
+  schemas:
+    ServerVersion:
+      type: object
+      properties:
+        version:
+          type: string
+          example: 2023.1.1
+        major:
+          type: integer
+          example: 2023
+        minor:
+          type: integer
+          example: 1
+        fix:
+          nullable: true
+          type: integer
+          example: 1
+        info_url:
+          nullable: true
+          type: string
+          example: "https://github.com/MerginMaps/mergin/releases/tag/2023.1"
diff --git a/server/mergin/app.py b/server/mergin/app.py
index 654d5c04..8910c6d1 100644
--- a/server/mergin/app.py
+++ b/server/mergin/app.py
@@ -177,6 +177,12 @@ def create_app(public_keys: List[str] = None) -> Flask:
         options={"swagger_ui": False, "serve_spec": False},
         validate_responses=True,
     )
+    app.add_api(
+        "api.yaml",
+        arguments={"title": "Mergin"},
+        options={"swagger_ui": False, "serve_spec": False},
+        validate_responses=True,
+    )
 
     app.app.config.from_object(SyncConfig)
     app.app.connexion_app = app
diff --git a/server/mergin/config.py b/server/mergin/config.py
index f633e171..8855b5a8 100644
--- a/server/mergin/config.py
+++ b/server/mergin/config.py
@@ -7,6 +7,8 @@
 
 from .version import get_version
 
+config_dir = os.path.abspath(os.path.dirname(__file__))
+
 
 class Configuration(object):
     # flask/connexion variables
@@ -107,3 +109,16 @@ class Configuration(object):
     # using gevent type of worker impose some requirements on code, e.g. to be greenlet safe, custom timeouts
     GEVENT_WORKER = config("GEVENT_WORKER", default=False, cast=bool)
     GEVENT_REQUEST_TIMEOUT = config("GEVENT_REQUEST_TIMEOUT", default=30, cast=int)
+    DIAGNOSTIC_LOGS_URL = config(
+        "DIAGNOSTIC_LOGS_URL",
+        default="",
+    )
+    DIAGNOSTIC_LOGS_DIR = config(
+        "DIAGNOSTIC_LOGS_DIR",
+        default=os.path.join(
+            config_dir, os.pardir, os.pardir, os.pardir, "diagnostic_logs"
+        ),
+    )
+    DIAGNOSTIC_LOGS_MAX_SIZE = config(
+        "DIAGNOSTIC_LOGS_MAX_SIZE", default=1024 * 1024, cast=int
+    )
diff --git a/server/mergin/controller.py b/server/mergin/controller.py
new file mode 100644
index 00000000..93824e68
--- /dev/null
+++ b/server/mergin/controller.py
@@ -0,0 +1,61 @@
+import json
+import logging
+import os
+from flask import abort, current_app, request
+from flask_login import current_user
+from magic import from_buffer
+import time
+
+import requests
+
+from .utils import save_diagnostic_log_file
+from .app import parse_version_string, db
+
+
+def get_latest_version():
+    """Parse information about available server updates from 3rd party service"""
+    try:
+        req = requests.get(current_app.config["STATISTICS_URL"] + "/latest-versions")
+    except requests.exceptions.RequestException:
+        abort(400, "Updates information not available")
+
+    if not req.ok:
+        abort(400, "Updates information not available")
+
+    data = req.json().get(current_app.config["SERVER_TYPE"].lower(), None)
+    if not data:
+        abort(400, "Updates information not available")
+
+    parsed_version = parse_version_string(data.get("version", ""))
+    if not parsed_version:
+        abort(400, "Updates information not available")
+
+    data = {**data, **parsed_version}
+    return data, 200
+
+
+def save_diagnostic_log():
+    """Save diagnostic logs"""
+    # if server is using external storage, we don't want to save logs
+    if current_app.config.get("DIAGNOSTIC_LOGS_URL"):
+        abort(404)
+
+    # check if plain text body is not larger than 1MB
+    max_size = current_app.config.get("DIAGNOSTIC_LOGS_MAX_SIZE")
+    if request.content_length > max_size:
+        abort(413)
+    # get body from request
+    body = request.get_data()
+    if not body:
+        abort(400)
+    if len(body) > max_size:
+        abort(413)
+    mime_type = from_buffer(body, mime=True)
+    if mime_type != "text/plain":
+        abort(400)
+
+    app = request.args.get("app")
+    username = current_user.username if current_user.is_authenticated else "anonymous"
+    save_diagnostic_log_file(app, username, body)
+
+    return "Log saved successfully", 200
diff --git a/server/mergin/stats/api.yaml b/server/mergin/stats/api.yaml
index 382da567..757351bd 100644
--- a/server/mergin/stats/api.yaml
+++ b/server/mergin/stats/api.yaml
@@ -6,22 +6,6 @@ info:
 servers:
   - url: /
 paths:
-  /v1/latest-version:
-    get:
-      summary: Fetch latest available server version
-      operationId: get_latest_version
-      responses:
-        "200":
-          description: Latest version info
-          content:
-            application/json:
-              schema:
-                $ref: "#/components/schemas/ServerVersion"
-        "400":
-          $ref: "#/components/responses/BadStatusResp"
-        "404":
-          $ref: "#/components/responses/NotFoundResp"
-      x-openapi-router-controller: mergin.stats.controller
   /app/admin/report:
     get:
       summary: Download statistics for server
@@ -50,7 +34,7 @@ paths:
               schema:
                 type: string
         "400":
-          $ref: "#/components/responses/BadStatusResp"
+          $ref: "#/components/responses/BadRequestResp"
         "404":
           $ref: "#/components/responses/NotFoundResp"
 components:
@@ -59,26 +43,5 @@ components:
       description: Authentication information is missing or invalid.
     NotFoundResp:
       description: Project not found.
-    BadStatusResp:
+    BadRequestResp:
       description: Invalid request.
-  schemas:
-    ServerVersion:
-      type: object
-      properties:
-        version:
-          type: string
-          example: 2023.1.1
-        major:
-          type: integer
-          example: 2023
-        minor:
-          type: integer
-          example: 1
-        fix:
-          nullable: true
-          type: integer
-          example: 1
-        info_url:
-          nullable: true
-          type: string
-          example: "https://github.com/MerginMaps/mergin/releases/tag/2023.1"
diff --git a/server/mergin/stats/config.py b/server/mergin/stats/config.py
index 795df286..cfd5b4d9 100644
--- a/server/mergin/stats/config.py
+++ b/server/mergin/stats/config.py
@@ -2,6 +2,7 @@
 #
 # SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-MerginMaps-Commercial
 
+import os
 from decouple import config
 
 
diff --git a/server/mergin/stats/controller.py b/server/mergin/stats/controller.py
index 4606f1e5..d58a4417 100644
--- a/server/mergin/stats/controller.py
+++ b/server/mergin/stats/controller.py
@@ -2,7 +2,6 @@
 #
 # SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-MerginMaps-Commercial
 
-from dataclasses import asdict
 import requests
 from flask import abort, current_app, make_response
 from datetime import datetime, time
@@ -12,7 +11,7 @@
 from mergin.stats.models import MerginStatistics, ServerCallhomeData
 
 from .config import Configuration
-from ..app import parse_version_string, db
+from ..app import db
 
 
 class CsvTextBuilder(object):
@@ -27,28 +26,6 @@ def write(self, row):
         self.data.append(row)
 
 
-def get_latest_version():
-    """Parse information about available server updates from 3rd party service"""
-    try:
-        req = requests.get(Configuration.STATISTICS_URL + "/latest-versions")
-    except requests.exceptions.RequestException:
-        abort(400, "Updates information not available")
-
-    if not req.ok:
-        abort(400, "Updates information not available")
-
-    data = req.json().get(current_app.config["SERVER_TYPE"].lower(), None)
-    if not data:
-        abort(400, "Updates information not available")
-
-    parsed_version = parse_version_string(data.get("version", ""))
-    if not parsed_version:
-        abort(400, "Updates information not available")
-
-    data = {**data, **parsed_version}
-    return data, 200
-
-
 @auth_required(permissions=["admin"])
 def download_report(date_from: str, date_to: str):
     """Download statistics from server instance"""
diff --git a/server/mergin/tests/fixtures.py b/server/mergin/tests/fixtures.py
index 6b83ecf9..7cff688e 100644
--- a/server/mergin/tests/fixtures.py
+++ b/server/mergin/tests/fixtures.py
@@ -3,6 +3,7 @@
 # SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-MerginMaps-Commercial
 
 import os
+import shutil
 import sys
 import uuid
 from copy import deepcopy
@@ -80,6 +81,9 @@ def teardown():
                 if p.storage is not None
             ]
             cleanup(flask_app.test_client(), dirs)
+            diagnostic_logs_dir = flask_app.config.get("DIAGNOSTIC_LOGS_DIR")
+            if os.path.exists(diagnostic_logs_dir):
+                shutil.rmtree(diagnostic_logs_dir)
 
     request.addfinalizer(teardown)
     return flask_app
diff --git a/server/mergin/tests/test_controller.py b/server/mergin/tests/test_controller.py
new file mode 100644
index 00000000..9a266832
--- /dev/null
+++ b/server/mergin/tests/test_controller.py
@@ -0,0 +1,131 @@
+import os
+from flask import url_for, current_app
+import json
+from unittest.mock import MagicMock, patch
+
+import requests
+
+from ..auth.models import User
+from ..app import db
+from .utils import Response
+
+
+def test_healthcheck(client):
+    # anonymous user
+    client.get(url_for("/.mergin_auth_controller_logout"))
+    client.application.config["WTF_CSRF_ENABLED"] = True
+    maint_file = current_app.config["MAINTENANCE_FILE"]
+    resp = client.post("/alive")
+    assert resp.status_code == 200
+    resp_data = json.loads(resp.data)
+    print(resp.headers)
+    print(resp_data)
+    assert "processing_time_ms" in resp_data
+    print(type(resp_data))
+    assert not resp_data["maintenance"]
+
+    # create maintenance mode
+    with open(maint_file, "w+"):
+        resp = client.post("/alive")
+        assert resp.status_code == 200
+        resp_data = json.loads(resp.data)
+        assert resp_data["maintenance"]
+    os.remove(maint_file)
+
+    # tests with invalid method
+    resp = client.get("/alive")
+    assert resp.status_code == 405
+
+    # mock some db issue
+    _connect = db.engine.connect
+    db.engine.connect = MagicMock(side_effect=Exception("Some db issue"))
+    resp = client.post("/alive")
+    assert resp.status_code == 500
+    # undo mock
+    db.engine.connect = _connect
+
+
+def test_server_updates(client):
+    """Test proxy endpoint to fetch server updates information"""
+    assert client.application.config["SERVER_TYPE"] == "ce"
+    url = "/v1/latest-version"
+
+    with patch("requests.get") as mock:
+        api_data = {
+            "ee": {"version": "2023.1.2", "info_url": "https://release-info.com"},
+            "ce": {"version": "2023.1.2", "info_url": "https://release-info.com"},
+        }
+        mock.return_value = Response(True, api_data)
+        resp = client.get(url)
+        assert resp.status_code == 200
+        assert resp.json["version"] == api_data["ce"]["version"]
+        assert resp.json["major"] == 2023
+        assert resp.json["minor"] == 1
+        assert resp.json["fix"] == 2
+
+        # remove fix version
+        api_data["ce"]["version"] = "2023.2"
+        resp = client.get(url)
+        assert resp.status_code == 200
+        assert resp.json["major"] == 2023
+        assert resp.json["minor"] == 2
+        assert resp.json["fix"] is None
+
+        # invalid response
+        del api_data["ce"]["version"]
+        resp = client.get(url)
+        assert resp.status_code == 400
+
+        # 3rd party api failure
+        mock.side_effect = requests.exceptions.RequestException("Some failure")
+        resp = client.get(url)
+        assert resp.status_code == 400
+
+
+def test_save_diagnostic_log(client, app):
+    """Test save diagnostic log endpoint"""
+    user = User.query.filter(User.username == "mergin").first()
+    url = url_for("mergin_controller_save_diagnostic_log")
+    resp = client.post(url)
+    assert resp.status_code == 400
+
+    # bad request
+    resp = client.post(url, data="test")
+    assert resp.status_code == 400
+
+    url = url_for("mergin_controller_save_diagnostic_log", app="test_app")
+
+    # too large request
+    max_size = app.config["DIAGNOSTIC_LOGS_MAX_SIZE"]
+    resp = client.post(url, data="x" * (max_size + 1))
+    assert resp.status_code == 413
+
+    # invalid mime type
+    resp = client.post(url, data="#!/usr/bin/python\n")
+    assert resp.status_code == 400
+
+    # valid request
+    resp = client.post(url, data="test")
+    assert resp.status_code == 200
+
+    # check if file was created
+    log_dir = app.config["DIAGNOSTIC_LOGS_DIR"]
+    assert os.path.exists(log_dir)
+    files = os.listdir(log_dir)
+    assert len(files) == 1
+    assert files[0].startswith(f"{user.username}_test_app_")
+    assert files[0].endswith(".log")
+    with open(os.path.join(log_dir, files[0]), "r") as f:
+        content = f.read()
+        assert content == "test"
+    os.remove(os.path.join(log_dir, files[0]))
+
+    # anonymous user
+    client.get(url_for("/.mergin_auth_controller_logout"))
+    # valid request
+    resp = client.post(url, data="test")
+    assert resp.status_code == 200
+    files = os.listdir(log_dir)
+    assert len(files) == 1
+    assert files[0].startswith(f"anonymous_test_app_")
+    assert files[0].endswith(".log")
diff --git a/server/mergin/tests/test_statistics.py b/server/mergin/tests/test_statistics.py
index 6f339505..189b04b0 100644
--- a/server/mergin/tests/test_statistics.py
+++ b/server/mergin/tests/test_statistics.py
@@ -2,16 +2,15 @@
 #
 # SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-MerginMaps-Commercial
 
-import csv
 from dataclasses import asdict
-from datetime import timedelta, timezone, datetime
+from datetime import timezone, datetime
 import json
 from unittest.mock import patch
 import requests
 from sqlalchemy.sql.operators import is_
 
 from mergin.auth.models import User
-from mergin.sync.models import Project, ProjectRole
+from mergin.sync.models import ProjectRole
 
 from ..app import db
 from ..stats.tasks import get_callhome_data, save_statistics, send_statistics
@@ -122,43 +121,6 @@ def test_send_statistics(app, caplog):
         assert info.last_reported
 
 
-def test_server_updates(client):
-    """Test proxy endpoint to fetch server updates information"""
-    assert client.application.config["SERVER_TYPE"] == "ce"
-    url = "/v1/latest-version"
-
-    with patch("requests.get") as mock:
-        api_data = {
-            "ee": {"version": "2023.1.2", "info_url": "https://release-info.com"},
-            "ce": {"version": "2023.1.2", "info_url": "https://release-info.com"},
-        }
-        mock.return_value = Response(True, api_data)
-        resp = client.get(url)
-        assert resp.status_code == 200
-        assert resp.json["version"] == api_data["ce"]["version"]
-        assert resp.json["major"] == 2023
-        assert resp.json["minor"] == 1
-        assert resp.json["fix"] == 2
-
-        # remove fix version
-        api_data["ce"]["version"] = "2023.2"
-        resp = client.get(url)
-        assert resp.status_code == 200
-        assert resp.json["major"] == 2023
-        assert resp.json["minor"] == 2
-        assert resp.json["fix"] is None
-
-        # invalid response
-        del api_data["ce"]["version"]
-        resp = client.get(url)
-        assert resp.status_code == 400
-
-        # 3rd party api failure
-        mock.side_effect = requests.exceptions.RequestException("Some failure")
-        resp = client.get(url)
-        assert resp.status_code == 400
-
-
 def test_save_statistics(app, client):
     """Test save statistics celery job"""
     info = MerginInfo.query.first()
diff --git a/server/mergin/tests/test_utils.py b/server/mergin/tests/test_utils.py
index f3249daa..514928ea 100644
--- a/server/mergin/tests/test_utils.py
+++ b/server/mergin/tests/test_utils.py
@@ -3,14 +3,18 @@
 # SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-MerginMaps-Commercial
 
 import base64
+from datetime import datetime
 import json
 import os
 import pytest
 from flask import url_for, current_app
 from sqlalchemy import desc
-from unittest.mock import MagicMock
+import os
+from unittest.mock import patch
+from pathvalidate import sanitize_filename
+
+from ..utils import save_diagnostic_log_file
 
-from ..app import db
 from ..sync.utils import (
     parse_gpkgb_header_size,
     gpkg_wkb_to_wkt,
@@ -109,36 +113,6 @@ def test_parse_gpkg():
     assert not wkt
 
 
-def test_healthcheck(client):
-    client.application.config["WTF_CSRF_ENABLED"] = True
-    maint_file = current_app.config["MAINTENANCE_FILE"]
-    resp = client.post("/alive")
-    assert resp.status_code == 200
-    resp_data = json.loads(resp.data)
-    assert "processing_time_ms" in resp_data
-    assert not resp_data["maintenance"]
-
-    # create maintenance mode
-    with open(maint_file, "w+"):
-        resp = client.post("/alive")
-        assert resp.status_code == 200
-        resp_data = json.loads(resp.data)
-        assert resp_data["maintenance"]
-    os.remove(maint_file)
-
-    # tests with invalid method
-    resp = client.get("/alive")
-    assert resp.status_code == 405
-
-    # mock some db issue
-    _connect = db.engine.connect
-    db.engine.connect = MagicMock(side_effect=Exception("Some db issue"))
-    resp = client.post("/alive")
-    assert resp.status_code == 500
-    # undo mock
-    db.engine.connect = _connect
-
-
 def test_is_name_allowed():
     test_cases = [
         ("project", True),
@@ -270,3 +244,33 @@ def test_get_x_accell_uri(client):
 
     url_parts = ()
     assert get_x_accel_uri(*url_parts) == "/download"
+
+
+def test_save_diagnostic_log_file(client, app):
+    """Test save diagnostic log file"""
+    # Mock datetime value
+    test_date = "2025-05-09T12:00:00+00:00"
+    app_name = "t" * 256
+    username = "test-user"
+    body = b"Test log content"
+    to_folder = app.config["DIAGNOSTIC_LOGS_DIR"]
+
+    saved_file_name = save_diagnostic_log_file(app_name, username, body)
+    saved_file_path = os.path.join(to_folder, saved_file_name)
+    assert os.path.exists(saved_file_path)
+    assert len(saved_file_name) == 255
+
+    with patch("mergin.utils.datetime") as mock_datetime:
+        mock_datetime.now.return_value = datetime.fromisoformat(test_date)
+        app_name = "test_<>app"
+        saved_file_name = save_diagnostic_log_file(app_name, username, body)
+        # Check if the file was created
+        assert saved_file_name == sanitize_filename(
+            username + "_" + app_name + "_" + test_date + ".log"
+        )
+        saved_file_path = os.path.join(to_folder, saved_file_name)
+        assert os.path.exists(saved_file_path)
+        # Check the content of the file
+        with open(saved_file_path, "r") as f:
+            content = f.read()
+            assert content == body.decode("utf-8")
diff --git a/server/mergin/utils.py b/server/mergin/utils.py
index c570acf5..9acc6124 100644
--- a/server/mergin/utils.py
+++ b/server/mergin/utils.py
@@ -3,9 +3,12 @@
 # SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-MerginMaps-Commercial
 import math
 from collections import namedtuple
-from datetime import timedelta
+from datetime import datetime, timedelta, timezone
 from enum import Enum
+import os
+from flask import current_app
 from flask_sqlalchemy import Model
+from pathvalidate import sanitize_filename
 from sqlalchemy import Column, JSON
 from sqlalchemy.sql.elements import UnaryExpression
 from typing import Optional
@@ -116,3 +119,19 @@ def format_time_delta(delta: timedelta) -> str:
         else:
             difference = "N/A"
     return difference
+
+
+def save_diagnostic_log_file(app: str, username: str, body: bytes) -> str:
+    """Save diagnostic log file to DIAGNOSTIC_LOGS_DIR"""
+
+    content = body.decode("utf-8")
+    datetime_iso_str = datetime.now(tz=timezone.utc).isoformat()
+    file_name = sanitize_filename(
+        username + "_" + app + "_" + datetime_iso_str + ".log"
+    )
+    to_folder = current_app.config.get("DIAGNOSTIC_LOGS_DIR")
+    os.makedirs(to_folder, exist_ok=True)
+    with open(os.path.join(to_folder, file_name), "w") as f:
+        f.write(content)
+
+    return file_name