Spelling and grammar checkers
If you are going to write an article or web page in Esperanto, it is important to check it for spelling and grammatical errors before submitting it for publication. You may need a spelling checker for a word processor and for a browser, and for an email programme. Each of these has to be set up separately. Generally this is only possible with Open Source Software because Esperantists can contribute programming and Esperanto word lists. Proprietary software does not generally supply Esperanto spelling or grammar checkers.
Word processors
The most suitable option is LibreOffice Writer. It is open source software and available free for Windows, Macintosh, and Linux computers and for Android devices. Instructions on how to install the LibreOffice suite are available at: https://www.libreoffice.org/get-help/install-howto/
When you have installed LibreOffice, you need to install an extension for checking Esperanto text. Open the LibreOffice Writer programme and use the menu: Tools > Extension Manager > Get more extensions online > enter Esperanto in the search box and choose an extension. There are two suitable extensions:
Esperanto spellchecker, thesaurus and hyphenizer
https://extensions.libreoffice.org/extensions/esperanto-spellchecker-thesaurus-and-hyphenizer
Download the extension and install it according to the instructions on the extensions page.
Language Tool
https://languagetool.org/download/LanguageTool-4.4.1.oxt
If you want this extension, download it and install it according to the instructions on the extensions page.
Set the document language
You can choose the default language to be used for each new document in Writer (or any of the other applications of LibreOffice). You can change the language to something else later if you need to.
To configure LibreOffice Writer to use Esperanto for all new documents by default, you can go to Tools > Options > Language settings > Languages > in the section Default languages for documents, Western choose Esperanto.
When you want to write a new document in Esperanto, or load an existing document in Esperanto, make sure the document language is set to Esperanto. To do that go to the menu: Tools > Language > For all text > Esperanto. You can then edit the document and the spelling will be checked automatically as you go.
Browsers
Open source browsers generally supply extensions for Esperanto. For example:
Firefox
Extensions: Grammar and Spell Checker – Language Tool
Languages: Esperanto Language Pack (Mozilla)
Add-on: LanguageTool Grammar and spell checker at https://addons.mozilla.org/en-US/firefox/addon/languagetool/
Chrome
Add-on: LanguageTool Grammar and spell checker at https://addons.mozilla.org/en-US/firefox/addon/languagetool/
This extension will check your text by sending it to LanguageTool.org over an encrypted connection. Your text will not be stored.
Edge
The new (2020) Microsoft Edge browser is based on the Chromium browser, so Edge can use Chromium add-ons, including LanguageTool, which allows you to spellcheck Esperanto text. Information at:
https://microsoftedge.microsoft.com/addons/detail/grammar-and-spell-checker/hfjadhjooeceemgojogkhlppanjkbobc
See the previous section.
Thunderbird
In Thunderbird choose menu Tools > Add-ons > Get Add-ons > Learn More > enter Esperanto in the search field and click on the search button. Choose the extension Esperanta Vortaro and install it.
Alternative method (tested in version 68.10.0): in Thunderbird choose menu Edit > Preferences > Download More Dictionaries > scroll to Esperanto, and click on Download Dictionary; in the window Add-ons it should display information about Esperanta Vortaro. Click the button +Add to Thunderbird > Add > Ok > close the window.
When you are writing a message, right click on the main text and choose Languages > Esperanto (or another language). Thunderbird then automatically checks your spelling while you type.
Stand-alone programmes on the web
Lingvohelpilo
When you have text that you want checked you can copy it and paste it into the text box at http://beta.visl.sdu.dk/lingvohelpilo/. Click on Kontroli to run the check. The results are sometimes useful but it misses some types of errors.
Language Tool
Go to https://languagetool.org/eo/ and paste your text there to check it. It will tell you where there seem to be errors, but does not try to guess how to correct them. It allows you to correct the errors and then copy the text for pasting somewhere else.
There is also a LanguageTool Browser Add-on at https://github.com/languagetool-org but we have not tested that.