KOReader on Kindle: KUAL, kindlepw2, and kindlehf

KOReader is an open-source document reader that runs on jailbroken Kindle hardware alongside — not instead of — Amazon's stock reader. It is launched from KUAL, the Kindle Unified Application Launcher, which the jailbreak installs as the entry point for community software. The install detail that most often goes wrong is package selection. KOReader ships two Kindle builds, split at firmware 5.16.3: - kindlepw2 — for Paperwhite 2 and newer models running firmware 5.16.2.1.1 or earlier, carrying compiler optimisations targeting those models. - kindlehf — for any Kindle running firmware 5.16.3 or newer. Choosing the wrong package produces a build that will not start. The split is a compiler and ABI boundary, not a feature difference, and it is keyed to firmware version rather than to the device's marketing name. Because kindlehf exists, "newer firmware means no KOReader" is false. Newer devices need a jailbreak that covers their band — see Kindle Jailbreak Landscape: LanguageBreak, WinterBreak, and AdBreak — but once jailbroken they run KOReader normally. What KOReader adds over the stock reader is control rather than raw reading quality. Amazon's reader has had many years of typography work behind it and is genuinely good at rendering a finished book. KOReader instead offers font and margin control, OPDS catalogue support, custom dictionaries, highlight and annotation export to Markdown and JSON, and KOSync, which synchronises reading position across devices including non-Kindle ones. That last item is the one Amazon structurally will not provide, because Whispersync does not extend personal documents to third-party applications. KOReader is also the rendering half of the fetch-and-render split described in Getting Web Serials onto an E-Reader: The EPUB Pipeline.