Can you name all of the extant Indo-European languages, according to Wikipedia?
Many, many speech varieties can be categorized as either languages or dialects. I've generally aired on the side of excluding things that Wikipedia refers to as dialects or varieties on their repective pages, but discretion has been used.
The hints are intended to be helpful moreso than a complete, comprehensive, and indisputable categorization.
In general, creoles, pidgins, intermediate dialects, cants, etc have been excluded due to being hard to categorize and due to the massive number of English- and French-based creoles spoken across the Caribbean, Africa, the Pacific, and parts of Asia.
In general, you can expect languages closer to each other on the list to be more closely related, but this is not universally true.
Many of the Oïl languages could be considered dialects of French, but are more distinct than other dialects
Judeo-Spanish is not the only Jewish-specific language listed as Indo-European, but it is not intelligible with Spanish, hence its inclusion
Asturian and Leonese are sometimes considered separate languages
Irish and Manx are also Gaelic languages, but less likely to be referred to as "Gaelic" in English
Luxembourgish is considered by Wikipedia to be a dialect in the Moselle Franconian continuum; however, I've included it as it is a national language
Of North, East, and West Frisian, only West Frisian is commonly called "Frisian"
Some dialects of Lithuanian/other Baltic languages spoken in Lithuania are hotly debated as dialects vs languages
Several Slavic languages which could also be described as pidgins or creoles have been excluded for consistency, since including all English- and French-based creoles would be infeasible
The Serbo-Croatian language(s) are divided more by politics than by language, although significant differences do exist, especially regarding Bosnian
Many languages in the Iranian and Indic families are hotly contested as languages, dialects, parts of dialect continua, registers, etc. I did my best
Zoroastrian Dari and Persian/Dari/Tajik are (at least) two different languages, but they share a name
Aer, along with several closely-related languages called "Koli," are difficult to categorize
Hindi and Urdu use different scripts and have substantial differences in vocabulary, but much of that vocabulary is loaned from Sanskrit or Persian and Arabic, respectively. Their underlying grammar and phonology lead to their classification as one language here
Awadhi and Fiji Hindi could be considered separate languages, or Fiji Hindi could be considered a dialect that developed in isolation
Chittagonian is sometimes referred to as a dialect of Bengali, but is generally not considered so by linguists
Hajong has been suggested to be a creole language, with an Indo-European substrate and a Tibeto-Burman superstrate, but this is not well-substantiated yet
Several languages exist as intermediate dialects of Marathi and Konkani, meaning they are not a dialect of either language but may integrate elements of both, and have been excluded
Judeo-Spanish is not the only Jewish-specific language listed as Indo-European, but it is not intelligible with Spanish, hence its inclusion
Asturian and Leonese are sometimes considered separate languages
Irish and Manx are also Gaelic languages, but less likely to be referred to as "Gaelic" in English
Luxembourgish is considered by Wikipedia to be a dialect in the Moselle Franconian continuum; however, I've included it as it is a national language
Of North, East, and West Frisian, only West Frisian is commonly called "Frisian"
Some dialects of Lithuanian/other Baltic languages spoken in Lithuania are hotly debated as dialects vs languages
Several Slavic languages which could also be described as pidgins or creoles have been excluded for consistency, since including all English- and French-based creoles would be infeasible
Many languages in the Iranian and Indic families are hotly contested as languages, dialects, parts of dialect continua, registers, etc. I did my best
Zoroastrian Dari and Persian/Dari/Tajik are (at least) two different languages, but they share a name
Aer, along with several closely-related languages called "Koli," are difficult to categorize
Hindi and Urdu use different scripts and have substantial differences in vocabulary, but much of that vocabulary is loaned from Sanskrit or Persian and Arabic, respectively. Their underlying grammar and phonology lead to their classification as one language here
Awadhi and Fiji Hindi could be considered separate languages, or Fiji Hindi could be considered a dialect that developed in isolation
Hajong has been suggested to be a creole language, with an Indo-European substrate and a Tibeto-Burman superstrate, but this is not well-substantiated yet
Several languages exist as intermediate dialects of Marathi and Konkani, meaning they are not a dialect of either language but may integrate elements of both, and have been excluded