pgadmin4 : postgresql application server could not be contacted.


I found the same issue when upgrading to pgAdmin 4 (v1.6). On Windows I found that clearing out the C:\Users\%USERNAME%\AppData\Roaming\pgAdmin folder fixed the issue for me. I believe it was attempting to use the sessions from the prior version and was failing. I know the question was marked as answered, but downgrading may not always be an option.

Note: AppData\Roaming\pgAdmin is a hidden folder.

We got the same issue. so no any change in the file. but start pgAdmin 4 using administrator.

The following step. 1. right click pgAdmin 4 icon 2. select "Run As Administrator"

I had the same issue on Windows 10, with a new installation of PostgreSQL 10.

I solved it by including the path C:\PostgreSQL\10\bin ({your path to postgresql}\bin) to system environment variables.

To access environment variables: Control Panel > System and security > System or right click on PC, then > Advance system settings > Environment variables > System variables > Path > Edit.


What finally worked was downgrading to pgadminIII-v.1.22:

if you are using Mac OS X here is a fix: Open terminal and run this command

pg_ctl -D /usr/local/var/postgres -l /usr/local/var/postgres/server.log restart

and for other OS just restart your Postgresql server, it will solve

Then start pgAdmin4, it will start as normal

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I had same issue on windows. I had v1.6 installed as well as v2.0. Uninstalling v1.6 allowed me to login.


I had the same problem, but running it as an admin worked.


Have you recently installed a new version of pgAdmin ?

This issue (and the misleading message) is simply due to the fact that old versions of pgAdmin are unable to read the settings saved by a newer version of pgAdmin !

Make sure you're starting the right version of pgAdmin (your shortcuts are likely to point to the old version !) and/or uninstall the old version: the upgrade wizard doesn't do it for you !

Akshata Dabade

Deleting the contents of C:\Users\%USERNAME%\AppData\Roaming\pgAdmin directory worked for me!


I use the cmd prompt on Windows 10 with psql postgres postgres.

Then I launch pgAdmin4 and it works.

I had this problem with pgadmin4 v2.1 on linux fedora 27

Solved by installing a missing dependency: python3-flask-babelex


I had the same issue on the macosx and I renamed .pgadmin (in /users/costa) to .pgadminx and I was able to start pgAdmin4.

In Windows Just go to this path and clear it ,that works !!


I've been dealing with this for awhile (frustrating). So much that I have instructions on my desktop consolidating all of these ideas. Here is my magic combination to the solution:

  1. Delete from App Data C:\Users\%USERNAME%\AppData\Roaming\pgAdmin
  2. Add to Path Variables C:\Program Files\PostgreSQL\9.6\bin (I actually added it to both user and system)
  3. Right click and start as admin.

You don't have to do this every time but when it gets out of wack try these steps.

If none of the methods help try checking your system and user environments PATH and PYTHONPATH variables.

I was getting this error due to my PATH variable was pointing to different Python installation (which comes from ArcGIS Desktop).

After removing path to my Python installation from PATH variable and completely removing PYTHONPATH variable, I got it working!

Keep in mind that python command will not be available from command line if you remove it from PATH.

I was able to solve the problem by changing the pgAdmin web interface port.

I believe this problem occurred on my computer because I have several other services consuming webs ports like qBittorrent, IDEJetbrains, etc.

Right-clicking on the pgAdmin logo near the clock is possible to configure it.

enter image description here

I Fixed it in windows 10 just running pgAdmin 4 as Run as Administrator .

It seems in most of the cases Postgres trying to use information from previous sessions to find/connect the server and failing. Clearing out the previous session info helped me, it is a combination of 2 already mentioned answers above:

  1. Navigate to Postgres session's folder "C:\Users\YourUsernameOrAdmin\AppData\Roaming\pgAdmin\sessions"
  2. Delete all the data from this folder.
  3. Start PgAdmin in administrator mode.


Got this issue after I upgraded PostgreSQL 9.4 to 9.6. The 9.4 binary package had PgAdmin 3 while 9.6 came with PgAdmin 4. I resolved it after a clean installation (I completely uninstalled and reinstalled) of PostgreSQL.

However, under different circumstances, you could try running the pgAdmin 4 application as an Administrator. This should fix the error.

downloaded pgadmin 4 v2.0 and install it no problem atm on force installation. try it. that was solution for me.

I need to add this here because I've had several issues with this message. If you have recently upgraded to High Sierra you will find the latest (pgadmin 4.20) will keep appearing with the message "Application Server Could Not be Contacted". What this actually means on Macs is that python was unable to configure your environment in ~/.pgadmin

This directory stores all the things you setup and configure and even logs of what was ran on your user copy usage of pgadmin.

The way to fix this issue on High Sierra is down to sqlite3. If you look in that directory you'll see everything is stored in sqlite3 files.

When version 4.20 of pgadmin was released it was shipped with a version later than sqlite3.19 and the problem arises because High Sierra is shipped with sqlite3.19, so to fix this issue, you need to replace the old version of sqlite3 with the latest on your packager.

Now be aware, MacosX+ all use sqlite to store details for the majority of apps on your mac, so you'll need to make sure you do not just wipe the old version but you'll have to have both versions co-existing together in harmony to avoid anything major occurring on your mac.

1) download brew

2) update brew and upgrade brew to make sure it's up-to-date

3) brew install sqlite3

4) mv /usr/bin/sqlite3 /usr/bin/sqlite3.os

5) ln -s /usr/local/Cellar/sqlite/3.21.0/bin/sqlite3 /usr/bin/sqlite3

6) /usr/bin/sqlite3 -version (check version is later than 3.19)

You can now proceed to open up pgadmin as normal

If you use older postgresql version like 9.x and its services is running,PgAdmin 4 confused which server is base database.

So stop the service older version or new one.Run PgAdmin 4 as Administrator

Its worked for me

For my case in Windows 10 for postgresql 10 version, it worked by changing SERVER_MODE to False in placed in web folder, as per these configuration settings:

There are other settings mentioned in this answer ( regarding python but I just changed SERVER_MODE and it worked.

Kill it in Windows Task Manager and then try again. It seems that there is some sort of a problem when accessing the server from different applications.

As for me on windows 2012r2 it's start to work only after I reinstall pgAdmin 4 to folder c:\pgAdmin4. With out spaces and any special chars. And all so I give full permission to this folder in NTFS.

It worked for me after installing python2.7 for pgAdmin 4 v2

Happens mostly when you have multiple versions of pgadmin installed or while trying to upgrade. Even I tried everything from killing the "running PID on port 5432" to "changing the server mode". In my case I uninstall postgres and re-install it again on different port(5433). Later, I opened it through cmd(right click on cmd and select "run cmd as an Administrator").enter image description here

I ran into this issue as well. Windows 10. I had older version of pgAdmin 4 (1.6) and 2.0. I guess both are older now.

In any case a complete uninstall of both versions and a reinstall of 2.0 worked.

You should downgrade to pgadmin3. It Worked for me on windows 10.1 with postrgreSQL 9.6.