# MT5 Python initialize() hangs: terminal build mismatch Independent and unofficial. Not affiliated with or endorsed by any broker or platform named here. Educational only: nothing here is advice, and nothing here recommends a broker or a trade. This is the markdown version of https://openbrokerapi.com/errors/mt5/initialize-hangs-build-mismatch, written from the same records as that page. Risk warning: CFDs and spread bets are complex instruments and come with a high risk of losing money rapidly due to leverage. You can lose money on these products, and each provider publishes its own loss figure under FCA rules. You should consider whether you understand how they work and whether you can afford to take the high risk of losing your money. Automated and API trading can amplify losses through bugs, connectivity failures and runaway orders. Your script calls mt5.initialize() and never gets past it: no True, no False, no error code. An MQL5 forum thread traced one case to two MetaTrader 5 builds that did not match. What that means and what to check. - Last reviewed: 2026-09-23 Unverified in part: carried over from an earlier version of this site. The links below are the sources it was written from, but its statements have not been re-read at source since the date shown, so check anything you rely on. ## What to check 1. In each MetaTrader 5 terminal on the machine, open Help, then About, and note its build. 2. Check which terminal your script starts. If there is more than one, pass the full path of the one you mean to `initialize(path=...)`. 3. If the builds differ, you have the situation the thread describes, and that is the first thing to resolve. 4. Check the terminal is build 4755 or later, the oldest MetaQuotes has supported since 1 Jul 2025. 5. Check the package: `pip show MetaTrader5` prints the installed version. The newest on PyPI when we read it was 5.0.6231, released 27 Sep 2026. 6. Print `mt5.last_error()` whenever initialize() returns False, so that if the call does come back you have a code to look up in the [MetaTrader 5 internal error codes](https://openbrokerapi.com/errors/mt5/internal-errors). The build mismatch is what the thread reports. The steps are checks we suggest to find out whether you have the same problem, not fixes reported in the thread. Next steps for this error - Every MetaTrader 5 endpoint No single endpoint is named for this error on this site. - [MetaTrader 5 quickstart](https://openbrokerapi.com/platforms/metatrader-5/quickstart) ## Why it happens The MetaTrader5 package connects to a running MetaTrader 5 terminal over interprocess communication, so the Python side and the terminal have to be able to talk to each other before initialize() can return. In the thread of 31 Aug 2025 the hang came with a mismatch between build 5233 and build 5238. The thread gives the two numbers. It does not give a general rule for which build to run, and neither do we. ## Questions ### Why does mt5.initialize() hang instead of returning an error? The MQL5 forum thread of 31 Aug 2025 does not explain the mechanism. What it reports is that the hang came with a build mismatch, 5233 against 5238. ### Which MetaTrader 5 build do I need for Python? MetaQuotes has supported terminals from build 4755 onwards since 1 Jul 2025. Above that minimum, the problem in the thread was two builds that did not match, not one build being too old. ### How do I see my MetaTrader 5 terminal build? In the terminal, open Help, then About. Check every copy installed on the machine, not only the one you open by hand. ### Does updating the MetaTrader5 package fix the hang? The thread does not say so. Compare the installed version from pip show MetaTrader5 with the newest on PyPI, 5.0.6231 of 27 Sep 2026, as one of the things you rule out. ## Sources - [MQL5 forum: Help request for MetaTrader5 initialization with Python](https://www.mql5.com/en/forum/494355)posted 31 Aug 2025, checked 21 Sep 2026 - [MQL5 docs: initialize](https://www.mql5.com/en/docs/python_metatrader5/mt5initialize_py)checked 20 Sep 2026 - [MQL5 docs: MetaTrader for Python](https://www.mql5.com/en/docs/python_metatrader5)checked 20 Sep 2026 - [PyPI: MetaTrader5](https://pypi.org/project/MetaTrader5/)checked 21 Sep 2026 - [MetaQuotes company news: end of support for older terminals](https://www.metaquotes.net/en/company/news/5479)checked 20 Sep 2026 ## More on the MetaTrader 5 API - [MetaTrader 5 API quickstart](https://openbrokerapi.com/platforms/metatrader-5/quickstart): From credentials to a first call on a demo account, step by step. - [MetaTrader 5 API error codes](https://openbrokerapi.com/errors/mt5): 311 decoded, each with what it means, and the fix where the source gives one. - [MetaTrader 5 functions](https://openbrokerapi.com/platforms/metatrader-5/functions): 78 documented, each with its signature, arguments, return value and source. - [MetaTrader 5 API page](https://openbrokerapi.com/platforms/metatrader-5): The full record: access, authentication, limits and the source for each. - [Claude with MetaTrader 5: a safe, read-first setup](https://openbrokerapi.com/guides/claude-mt5): Guide - [MetaTrader 5 for Python: which platforms does it run on?](https://openbrokerapi.com/guides/metatrader-5-python-platforms): Guide - [MT5 trade history to a spreadsheet with Python](https://openbrokerapi.com/guides/mt5-trade-history-to-a-spreadsheet): Guide ## Licence and how to cite The records behind this page are all rights reserved. This file is the page itself, at its own address, in another format. It is not part of the CC BY 4.0 downloads listed at https://openbrokerapi.com/data. Quote from it with a link to the page. Cite as: MT5 Python initialize() hangs: terminal build mismatch. Broker API Hub, https://openbrokerapi.com/errors/mt5/initialize-hangs-build-mismatch, newest check 2026-09-23. Where you rely on a single figure, cite the source and the checked date printed beside it as well. Where this page and a broker's own documentation differ, the documentation wins.