| Saami Southern | 1 | uTalk | uTalk |
| Sami | 1 | Tandem | Tandem |
| Samoan | 6 | Talkpal, or a tutor on italki | Drops, italki, Readlang, Talkpal, Tandem, uTalk |
| Sango | 1 | Tandem | Tandem |
| Sanskrit | 3 | uTalk, or a tutor on italki | italki, Readlang, uTalk |
| Sanskrit for Yoga | 1 | Drops | Drops |
| Sanskrit, Saṁskṛtam | 1 | Tandem | Tandem |
| Santali | 1 | Tandem | Tandem |
| Saraiki | 1 | Tandem | Tandem |
| Sardinian | 2 | uTalk | Tandem, uTalk |
| Scots | 2 | uTalk | Tandem, uTalk |
| Serbian | 16 | Ling, or a tutor on italki | Clozemaster, Dinolingo, Drops, Glossika, italki, Language Reactor, Ling, LingoHut, LingQ, Mango Languages, Readlang, Talkpal, Tandem, Teacher AI, Transparent Language Online, uTalk |
| Sesotho | 2 | Talkpal | Readlang, Talkpal |
| Sesotho sa Leboa | 1 | Talkpal | Talkpal |
| Setswana | 1 | Talkpal | Talkpal |
| Seychellois Creole | 1 | Tandem | Tandem |
| Shanghainese | 3 | Mango Languages | Mango Languages, Tandem, uTalk |
| Shona | 3 | uTalk | Readlang, Tandem, uTalk |
| Sicilian | 3 | Talkpal | Talkpal, Tandem, uTalk |
| Silesian | 1 | Talkpal | Talkpal |
| Sindhi | 5 | Talkpal, or a tutor on italki | italki, Readlang, Talkpal, Tandem, uTalk |
| Sinhala | 7 | Ling, or a tutor on italki | italki, Ling, Preply, Readlang, Talkpal, Tandem, uTalk |
| Sioux | 1 | Tandem | Tandem |
| Slovak | 16 | Ling, or a tutor on italki | Clozemaster, Dinolingo, Glossika, italki, Language Reactor, Ling, LingoHut, LingQ, Mango Languages, Mondly, Readlang, Talkpal, Tandem, Teacher AI, Transparent Language Online, uTalk |
| Slovenian | 15 | Ling, or a tutor on italki | Clozemaster, Dinolingo, Glossika, italki, Language Reactor, Ling, LingoHut, LingQ, Memrise, Preply, Readlang, Talkpal, Tandem, Teacher AI, uTalk |
| Somali | 7 | Ling, or a tutor on italki | italki, Ling, Readlang, Talkpal, Tandem, Transparent Language Online, uTalk |
| Sorbian | 1 | Ling | Ling |
| Southern Ndebele | 1 | Tandem | Tandem |
| Southern Sotho | 2 | uTalk | Tandem, uTalk |
| Spanish | 63 | Duolingo, or a tutor on italki | Assimil, Babbel, BaseLang, Beelinguapp, Busuu, Clozemaster, Coffee Break Spanish, Dinolingo, Dreaming Spanish, Drops, Duolingo, Endless Spanish, Fluent Forever, FluentU, Glossika, Gus on the Go, Gymglish, HelloTalk, italki, Jiveworld, Jumpspeak, Kwiziq, Langotalk, Langua, Language Reactor, Language Transfer, Ling, Lingoda, LingoDeer, LingoHut, Lingopie, LingQ, Lingvist, Mango Languages, Memrise, Michel Thomas Method, Migaku, Mondly, MosaLingua, News in Slow, Ouino, Pimsleur, Pingo AI, Praktika, Preply, Promova, Readlang, Readle, Rockalingua, Rocket Languages, Rosetta Stone, SpanishDict, Speak, Speakly, StoryLearning, Studycat, Talkpal, Tandem, Teacher AI, Transparent Language Online, Univerbal, uTalk, Yabla |
| Spanish Argentinian | 1 | uTalk | uTalk |
| Spanish Sign Language | 1 | Tandem | Tandem |
| Sranan Tongo | 1 | Tandem | Tandem |
| Sundanese | 4 | Ling | Ling, Readlang, Talkpal, Tandem |
| Swahili | 19 | Duolingo, or a tutor on italki | Clozemaster, Dinolingo, Drops, Duolingo, Glossika, italki, Language Transfer, Ling, LingoHut, LingQ, Mango Languages, Memrise, Pimsleur, Readlang, Talkpal, Tandem, Teacher AI, Transparent Language Online, uTalk |
| Swati | 1 | Talkpal | Talkpal |
| Swazi | 1 | Tandem | Tandem |
| Swedish | 34 | Duolingo, or a tutor on italki | Babbel, Beelinguapp, Clozemaster, Dinolingo, Drops, Duolingo, Glossika, Gus on the Go, italki, Jumpspeak, Langotalk, Langua, Language Reactor, Ling, LingoHut, LingQ, Lingvist, Mango Languages, Memrise, Michel Thomas Method, Mondly, Pimsleur, Pingo AI, Preply, Readlang, Rosetta Stone, Speakly, StoryLearning, Talkpal, Tandem, Teacher AI, Transparent Language Online, Univerbal, uTalk |
| Sylheti | 1 | Tandem | Tandem |
| Syriac | 1 | Tandem | Tandem |