diff --git a/constants.py b/constants.py
index 0057942..59b0656 100644
--- a/constants.py
+++ b/constants.py
@@ -52,6 +52,8 @@ class Messages:
     NO_CONNECTION_MSG        = "Unable to establish an internet connection."
     BAD_DOWNLOAD             = "Something went wrong"
     BAD_DOWNLOAD_MSG         = "Something went wrong with the downaload.\nCheck your internet connection and try again."
+    SLOW_CONN                = "Slow internet connection"
+    SLOW_CONN_MSG            = "Your internet connection is unstable or too slow."
 
 
 class Signal:
diff --git a/deploy/Linux/requirements_lin.txt b/deploy/Linux/requirements_lin.txt
index e4d9f51..98560a7 100644
--- a/deploy/Linux/requirements_lin.txt
+++ b/deploy/Linux/requirements_lin.txt
@@ -1,6 +1,7 @@
-pandas==0.24.2
-aiohttp==3.5.4
-pygame==1.9.6
-QtAwesome==0.5.7
-urllib3==1.24.2
-PyQt5==5.12.2
+pandas>=0.24.2
+certifi>=2019.6.16
+aiohttp>=3.5.4
+pygame>=1.9.6
+QtAwesome>=0.5.7
+urllib3>=1.25.3
+PyQt5>=5.12.3
diff --git a/deploy/Windows/requirements_win.txt b/deploy/Windows/requirements_win.txt
index 2b1e420..98560a7 100644
--- a/deploy/Windows/requirements_win.txt
+++ b/deploy/Windows/requirements_win.txt
@@ -1,36 +1,7 @@
-aiohttp==3.5.4
-altgraph==0.16.1
-asn1crypto==0.24.0
-async-timeout==3.0.1
-attrs==19.1.0
-certifi==2019.3.9
-cffi==1.11.5
-chardet==3.0.4
-cryptography==2.3.1
-Cython==0.29.6
-future==0.16.0
-idna==2.7
-intel-openmp==2019.0
-macholib==1.11
-multidict==4.5.2
-numpy==1.15.2
-pandas==0.23.4
-pefile==2018.8.8
-pycparser==2.19
-pydub==0.23.0
-pygame==1.9.4
-PyInstaller==3.4
-pyOpenSSL==18.0.0
-PyQt5==5.10.1
-PySocks==1.6.8
-python-dateutil==2.7.3
-pytz==2018.5
-pywin32-ctypes==0.2.0
-QtAwesome==0.5.0
-QtPy==1.5.1
-sip==4.19.8
-six==1.11.0
-urllib3==1.24
-win-inet-pton==1.0.1
-wincertstore==0.2
-yarl==1.3.0
+pandas>=0.24.2
+certifi>=2019.6.16
+aiohttp>=3.5.4
+pygame>=1.9.6
+QtAwesome>=0.5.7
+urllib3>=1.25.3
+PyQt5>=5.12.3
diff --git a/download_window.py b/download_window.py
index 7d16728..763cdc8 100644
--- a/download_window.py
+++ b/download_window.py
@@ -37,6 +37,10 @@ class DownloadWindow(QWidget, Ui_Download_window):
                                            text=Messages.BAD_DOWNLOAD_MSG,
                                            connection=self.close)
 
+        self._slow_conn_msg = pop_up(self, title=Messages.SLOW_CONN,
+                                     text=Messages.SLOW_CONN_MSG,
+                                     connection=self.close)
+
         self._download_thread = DownloadThread()
         self._download_thread.finished.connect(self._wait_close)
         self._download_thread.progress.connect(self._display_progress)
@@ -49,7 +53,12 @@ class DownloadWindow(QWidget, Ui_Download_window):
 
     def _downlaod_format_str(self, n, speed):
         """Return a well-formatted string with downloaded MB and speed."""
-        return f"Downloaded: {n} MB\nSpeed: {speed} MB/s"
+        ret = f"Downloaded: {n} MB\nSpeed: "
+        if speed == 0.0:
+            ret += "VERY SLOW"
+        else:
+            ret += f"{speed} MB/s"
+        return ret
 
     def show(self):
         """Extends QWidget.show. Set downloaded MB and speed to zero."""
@@ -86,6 +95,8 @@ class DownloadWindow(QWidget, Ui_Download_window):
             self._no_internet_msg.show()
         elif self._download_thread.status is ThreadStatus.BAD_DOWNLOAD_ERR:
             self._bad_db_download_msg.show()
+        elif self._download_thread.status is ThreadStatus.SLOW_CONN_ERR:
+            self._slow_conn_msg.show()
         else:
             self.close()
 
diff --git a/threads.py b/threads.py
index fc0a122..ed965f6 100644
--- a/threads.py
+++ b/threads.py
@@ -4,7 +4,7 @@ from io import BytesIO
 from math import ceil
 import os.path
 from shutil import rmtree
-from time import time
+from time import perf_counter
 from zipfile import ZipFile
 import aiohttp
 import urllib3
@@ -21,6 +21,11 @@ class ThreadStatus(Enum):
     UNKNOWN_ERR       = auto()
     BAD_DOWNLOAD_ERR  = auto()
     UNDEFINED         = auto()
+    SLOW_CONN_ERR     = auto()
+
+
+class _SlowConnError(Exception):
+    pass
 
 
 class BaseDownloadThread(QThread):
@@ -41,7 +46,7 @@ class DownloadThread(BaseDownloadThread):
     """Subclass BaseDownloadThread. Download the database, images and audio samples."""
 
     progress = pyqtSignal(int, float)
-    _CHUNK = 512 * 1024
+    _CHUNK = 128 * 1024
     _MEGA = 1024**2
 
     def __init__(self):
@@ -82,35 +87,38 @@ class DownloadThread(BaseDownloadThread):
                 preload_content=False,
                 timeout=4.0
             )
+            start = perf_counter()
             while True:
-                start = time()
                 try:
                     data = self._db.read(self._CHUNK)
                 except Exception:
-                    raise
+                    raise _SlowConnError
                 else:
-                    delta = time() - start
+                    delta = perf_counter() - start
                     if not data:
                         break
                     raw_data += data
                     self.progress.emit(
                         self._pretty_len(raw_data),
-                        self._get_download_speed(data, delta)
+                        self._get_download_speed(raw_data, delta)
                     )
                     if self._exit_call:
                         self._exit_call = False
                         self._db.release_conn()
                         return
-        except Exception:  # No internet connection.
+        except Exception as e:  # No (or bad) internet connection.
             self._db.release_conn()
-            self.status = ThreadStatus.NO_CONNECTION_ERR
+            if isinstance(e, _SlowConnError):
+                self.status = ThreadStatus.SLOW_CONN_ERR
+            else:
+                self.status = ThreadStatus.NO_CONNECTION_ERR
             return
         if self._db.status != 200:
             self.status = ThreadStatus.BAD_DOWNLOAD_ERR
             return
         try:
             is_checksum_ok = checksum_ok(raw_data, ChecksumWhat.FOLDER)
-        except Exception:
+        except Exception:  # checksum_ok unable to connect to the reference.
             self.status = ThreadStatus.NO_CONNECTION_ERR
             return
         else: