Breaking Changes

• BREAKING: "i2s.h" removed, I2S library added (#8108)

Core

• Make String reallocation warning more descriptive (#8131)
• Normalize core header's include guard. (#8110)
• makeword: sync header and implementation (#8097)
• Use optimal bundled library names (#8088) (#8098)
• Added IRAM_ATTR to _stopPWM() so that digitalWrite() would work inside ISR. Fixes #8043 (#8044) (#8048)
• makecorever.py: restore ARDUINO_ESP8266_GIT_VER even without .git/ (#8138)

IDE

• Update debug level list link (#8172)
• Add missing menu.UploadTool name definition (#8153)

Libraries - LittleFS

• Re-add mklittlefs to package.json, fixing "ESP8266 LittleFS Data Upload" (#8060)
• Don't crash when including LittleFS.h w/no FS (#8173)

Libraries - SD/SDFS

• SDFS: fix AvailableForWrite: do not always return 0 when space is available (#8167)

Libraries - ESP8266httpUpdate

• ESP266httpUpdate: remove dead API and fix doc (#8063)

Libraries - ESP8266WiFi

• Fix stopAllExcept with WiFiClientSecure (#8136)
• LwipIntfDev.h - apply static DNS config (#8076)

Libraries - SoftwareSerial

• Update EspSoftwareSerial to bug fix release 6.12.6

Libraries - ESP8266HTTPClient

• ESP8266HTTPClient: remove old example (#8111)
• Change protocol detection so uppercase or lowercase works (#8137)

Toolchain

• Update toolchain to gcc 10.3 w/patches (#8104) (#8103)
• Update toolchain to fix pgm_read_float_unaligned (#8091)
• Remove include and lib folders removed since 3.0.0 core (#8125)
• Add errors on invalid/missing function return type (#8165)
• GNU source: honoring libc requirements (#8147)

PlatformIO

• PIO: use CCFLAGS for -Werror (#8175) (#8092)
• Documentation: Note about options on PIO (#8174)

Documentation

• Fix readthedoc python dependencies (#8166)
• Documentation: Arduino IDE options: fix hyperlinks and format, options (#8158) (#8154)

CI / Release / Environment

• Add code-spell spelling checks to CI (#8067)
• Release script: protect bash variables and add logs, major/minor/rev macro addition, BASH fix (#8074) (#8126) (#8127) (#8168)
• Remove some no longer applicable artifacts from .gitignore (#8170)

Release 3.0.0 Notes

Great additions

• PoC cache configuration control (aka +16KB heap!) (#7060)
• Hardware WDT Stack Dump Tool (#7010)
• Update to GCC 10.2 (#7607)

Breaking: Deprecation - Removal

• BREAKING: httpclient: remove deprecated API (#7617)
• BREAKING: Update Arduino.h, remove TIM_DIV265 (#7440)
• BREAKING: Remove lwip-v1.4 specific code (#7436)
• BREAKING: Remove axTLS from code and documentation (#7437)

Breaking changes summary

• BREAKING: WString: return bool instead of unsigned char (#7939)
• BREAKING: wifi: remove pseudo-modes for shutdown, expose ::[resumeFrom]shutdown() (#7956)
• BREAKING: Disable WiFi at boot by default (#7902, #7990, #7993)
• BREAKING: base64::encode() compat with esp32: no newlines by default (#7910)
• BREAKING: Use IRAM_ATTR in place of ICACHE_RAM_ATTR (#7921)
• BREAKING: Upgrade to upstream newlib 4.0.0 release (64 bits time_t) (#7708)
• BREAKING: Change servo defaults to safer defaults (#7023)
• BREAKING: Add Print::availableForWrite method (#7658)
• BREAKING: Change return EEPROM.end() to bool (#7630)
• BREAKING: Change return type of channel() (#7656)
• BREAKING: Change return type of RSSI() (#7657)
• BREAKING: Add Wrong Password wifi status case (#7652)
• BREAKING: analogWriteRange 8-bit default (#7456)
• BREAKING: HTTPClient: RequestHandler: Pass String by const reference (#6583)

Boot

• eboot: .RODATA, upstream uzlib, move CRC, save 112 bytes (#7844)
• Update eboot to build with C17, not C99 standard (#7837, #7838)
• Fix eboot crash with exception 28. ets_printf() should take pointer argument. (#7666)
• Use 32b loads to set print strings (#7545)
• Comment out verify step in eboot.c (#7468)

Core

• BREAKING: WString: return bool instead of unsigned char (#7939)
• ESP class should be a singleton: make all member functions static. (#8006)
• Updated HWDT to use IRAM_ATTR instead of ICACHE_RAM_ATTR. (#8013, #8018)
• Hardware WDT Stack Dump Tool (#7010)
• WString: direct operator overloads instead of StringSumHelper (#7781)
• Clean up ICACHE_RAM_ATTR in VM PR (#7924)
• Added ESP32 compatible methods for setting/getting sleep mode (#7901)
• Enable 128K virtual memory via external SPI SRAM (#6994)
• Stream::send() (#6979, #7935, #7951, #7987, #7995)
• [BREAKING] base64::encode() compat with esp32: no newlines by default (#7910)
• BREAKING - Use IRAM_ATTR in place of ICACHE_RAM_ATTR (#7921)
• OOM debug: warn about String reallocation (#7908)
• OOM: avoid warn when calling *alloc(0) (#7909)
• String: add missing long long operator implementations (#7888)
• Support to reboot into UART download mode (#7854, #7897)
• String: compatibility with 64 bits scalars (#7863)
• Update toolchain to support std::remainder (#7849)
• allow to set pin to OUTPUT_OPEN_DRAIN in analogWriteMode (#7841)
• Add 24-bit mode to I2S (#7835)
• Hexdump fix&update (#7831)
• improve silicon aes_unwrap (#7773)
• Supersede #3856, remove undef min/max (#7824)
• Add stub for analogReference() (#7809)
• UART: add yield (#7799)
• BREAKING - Upgrade to upstream newlib 4.0.0 release (#7708)
• Update to latest uzlib upstream (#7776, #7782)
• i2s: adds i2s_rxtxdrive_begin(enableRx, enableTx, driveRxClocks, driveTxClocks) (#7748)
• PoC cache configuration control (#7060, #7754, #7767, #7768, #7812, #7816, #7820, #7790)
• Receiving no data in Updater is an error (#7729)
• PROGMEM compatibility changes to String (#7724)
• schedule_recurrent_function_us should be in iram (#7713)
• Re-implement PWM generator (#7715, #7712, #7022, #7231, #7800, #7996)
• WString: Optimize a bit (#7553)
• Fix sntp_get_real_time prototype in header (#7707)
• Provide String::indexOf for a char* needle (#7706)
• Fix newlib to support <+-nn> timezone names (#7699, #7702)
• BREAKING: Add Print::availableForWrite method (#7658)
• settimeofday_cb: distinguish from user or sntp (#7637)
• Add Copyright notice to Schedule.h (#7653)
• BREAKING: Add Wrong Password wifi status case (#7652)
• New flash writing method with offset/memory/size alignment handling (#7514)
• Add missing sntp_init/sntp_stop (#7628)
• Use direct member initialization instead of ctr initialisation (#7558)
• Prevent rewriting Updater_Signing.h if content unchanged (#7627)
• WString: c_str() returns null pointer after move (#7611)
• WString: mark move ctor as noexcept (#7610)
• sntp: use one time source and fix unsynchronized sntp time stamp (#7595)
• Add clear method to IPAddress (#7586)
• Check also if IP is not IPADDR_NONE (#7585)
• Fix gzip+signed OTA error (#7577)
• new w/ OOM now aborts by defaults, or throw an exception (#7536)
• getCpuFreqMHz(): fix when F_CPU is not defined (#7554)
• Updater MD5 cleanup on begin (#7534)
• Add synthetic IntegerDivideByZero exception (#7496)
• avoid circular #include dependence for PolledTimeout (#7356)
• base64 class uses String, adding harmless #include (#7517)
• sys/pgmspace.h: Refactor inline asm (#7510)
• Add SerialEvent() callback to loop processing (#7505)
• Remove warnings when building NoAssert (#7499)
• BREAKING - analogWriteRange 8-bit default (#7456)
• BREAKING - Pass String by const reference [3.0] (#6583)

Libraries - softserial

• Maintenance release 6.12.3: better dependency declarations for Platformio (#8030)
• EspSoftwareSerial 6.12.2: Inlining push() functions that must be in IRAM for calling from ISRs (#7986)
• Bug-fix release 6.12.1: a documentation error was reported by a user; dropped bit-patterns that masked the stop-bit fixed. (#7938)
• EspSoftwareSerial minor release 6.12.0 completes adaptation to new Stream::send() (#7923)
• Minor EspSoftwareSerial release 6.11.7, for deprecated ICACHE_RAM_ATTR in upcoming ESP8266 Arduino core 3.0.0. (#7922)
• EspSoftwareSerial, bump up Arduino library manager related files 6.11.6 (#7891)
• Update to EspSoftwareSerial 6.11.5 (#7889)
• EspSoftwareSerial bug-fix release 6.11.4 (#7862)
• Update to EspSoftwareSerial 6.11.3: prepares for ESP8266 Arduino core PR 6979. (#7840)
• EspSoftwareSerial 6.11.2: Delegate<> assign operators added. (#7815)
• Minor EspSoftwareSerial release 6.11.1 (#7804)
• Minor EspSoftwareSerial release 6.11.0 (#7802)
• EspSoftwareSerial bug fix release 6.10.1: preciseDelay() could delay() for extremely long time, if period duration was exceeded on entry. (#7771)
• EspSoftwareSerial 6.10.0: override keyword for recent Print::availableForWrite() addition (#7710)
• EspSoftwareSerial 6.9.0: data/strings in flash alignment handling fix. Yielding during write() improvement. (#7604)

Libraries - FS

• Update mklittlefs executable (#7906)
• Track creation time of LittleFS FS (#7873)
• Invalid read return value fix (#7817)
• Update to SdFat 2.0.2, speed SD access (#7779)
• Rationalize File timestamp callback (#7785)
• Update to LittleFS v2.3 (#7787)

Libraries - Network

• added ArduinoWiFiServer with send-to-all-clients functionality (#7612)
• internal: rename ClientContext::wait_until_sent() to wait_until_acked() (#7896)
• Added ESP32 compatible methods for setting/getting hostname (#7900)
• AP & dhcp-server: fix uninitialized variables (#7905)
• Netdump: Avoid UB and abort on nullptr buffer (#7822)
• lwip2: use pvPortXalloc/vPortFree and "-free -fipa-pta" (#7793)
• more lwIP physical interfaces (#6680)
• Netump (#7527, #7659)
• replace old Ethernet Arduino-library with v2, submoduled (#6812)

Library - WiFi

• WiFi: clean up AP SSID setter & getter, support 32 chars (#7941)
• [BREAKING] wifi: remove pseudo-modes for shutdown, expose ::[resumeFrom]shutdown() (#7956)
• [BREAKING] Disable WiFi at boot by default (#7902)
• Added broadcastIP method to WiFiSTA class (#7899)
• WIFI_RESUME improve speed and example (#7877)
• WiFiServer.cpp: Fix warning (#7755)
• update documentation example (#7697)
• Refactor WiFi scan example (#7655)
• BREAKING: Change return type of channel() (#7656)
• BREAKING: Change return type of RSSI() (#7657)
• Reduce codesize of setOutputPower (#7572)

Library - TLS/SSL

• Fix a warning (#8014)
• Adding comment to ignore SSL certificate in sample code. (#7994)
• Update Root Certificate in example (#7932)
• Adds the method setSSLVersions() also to WiFiClientSecure in order to use that new feature. (#7925)
• Add setSSLVersion call to SSL object (#7920)
• Allow users to inherit and override CertStore (#7827)
• Reduce BearSSL code size by not -O2 FSMs (#7807)
• WiFiServerSecure: Cache SSL sessions (#7774)
• WiFiClientSecure: use context (#7680)
• Update to latest BearSSL as of Nov 2020 (#7732)
• Add Stream loaders for BearSSL (#7675)
• Catch and display SSL errors for fatal alerts (#7681)
• Fix error when debug enabled but no port chosen (#7648)
• Remove stray axtls refs, deprecated compat funcs (#7626)
• Fix error message typo (#7581)
• Update DigestAuthorization.ino (Simple example update) (#7579)
• Update certs-from-mozilla.py (#7573, #7578)
• Use root cert, not fingerprint for api.github.com (#7490)
• Update FP for tls.mbed.org (#7479)
• Change BSSL_CertStore test URL (#7370)
• Update to BearSSL version lost in GCC10 update (#7453)

Library - Webserver

• ESP8266WebServer: Add variadic template version of collectHeaders() (#7296)
• Fix header FSM in webserver, fix Windows uploads (#7805)
• ETag support for WebServer (#7709)
• Rewrite multipart boundary detection (#7728)
• Fixed bug in parsing POST file uploads (#7543)
• Fix long password validation in WebServer (#7676)
• FIX MIME-Type for txt-suffix (#7608)
• FIX StaticRequestHandler crashes when cache_header is null and DEBUG_ESP_CORE is enabled (#7609)
• Avoid #includes with a surrounding namespace (#7560)
• webserver hook: allow to handle external http protocol (#7459, #7492, #7515)
• Made ESP8266WebServer::client() return a reference (fixes #7075) (#7080)
• WebServer: Allow client to send many requests on the same connection (#7414)
• webserver: do not count "plain" in argument list (#6768)
• webserver: string optimization (#7446)

Libraries - others

• Resolve "PWM-locked" / "phase-locked" waveform merge leftover in Servo lib (#7978)
• Add I2S class support (#7874)
• At MDNS.end() also release services (#7859)
• AVRISP: Prevent nullptr dereference on OOM (#7823)
• HTTPClient: fix error handling (#7811)
• LEAmDNS: one instance for all interfaces (#7786 - #7540 #7615 #7636 #7640)
• Add the missing 'rename' method wrapper in SD library. (#7766)
• Update to ESP8266HTTPClient.cpp for no Content-Length (#7691)
• BREAKING: Change servo defaults to safer defaults (#7023)
• Hook up custom timestamp proc for SD/SDFS (#7686)
• BREAKING: Change return EEPROM.end() to bool (#7630)
• httpclient: remove deprecated API (#7617)
• Avoid float-double-conversion (#7559)
• Use direct member initialization instead of ctr initialisation (#7556)
• Basic authentication with ESP8266httpUpdate (#7190)

Documentation

• doc: analogRead must not be called to frequently with WiFi is on (#7981)
• comments in ClientContext::connect() (#7961)
• Fix typo in EEPROM debug message (#7934)
• Fix link to ESP8266 NonOS SDK (#7914)
• Update a02-my-esp-crashes.rst (#7739)
• Clarified implementation of the signed OTA implementation (#7736)
• Specify where Additional Boards Manager URLs is (#7733)
• update documentation example (#7697)
• Revive a dead link (#7679)
• Update OTA HTTP Server Header Information (#7633)
• Pull deprecated axtls link (#7624)
• Update README.md (#7623)
• Update path of gdb (#7603)
• Fixup weird combination of oneline/multi line comments (#7566)
• Fix spelling typo under doc/faq (#7538)
• doc: gcc handles duplicate literal strings (#7531)
• Fix and add details to Serial doc (#7521)
• Fix spelling typos in files under doc/esp8266wifi (#7520)
• Typo (#7502)
• Mention OTA Update class blocks flash mode changes (#7321)
• Fix spelling typos in readme.rst (#7447)
• Grammar fixes (#7441)

CI

• Fix ESP8266SdFat architecture, Windows CI (#7866)
• upgrade arduino in CI (#7716)
• Use smarter cache key, cache Arduino IDE (#7791)
• Remove Travis-CI configuration (#7674)
• Allow test framework to use cores/esp8266/Arduino.h directly (#7377)
• ci: apt update (#7596)
• Properly replace toolchain in PlatformIO CI script (#7580)
• PIO: Delete owner field (#7563)
• Add CI test for eboot build (#7546)
• Update PIO CI to be less chatty, fix CI fail (#7530)
• CI: on host: force 64 bit mode like make -j2 CI implicitly does (#7513)
• Add valgrind mocked test to CI (#7501)
• Clean up minor warnings from LGTM.com (#7500)
• Small update to ease manual release generation (#7467)
• Fix typo in platform.txt causing device test fails (#7463)
• Transition from TravisCI to GitHub CI (#7444)
• Fix spelling typos in files under packages dir (#7439)
• Remove wget dump during CI (#7438)

Build options

• board manager: wemos d1 clones: new entry with menus for flash mode and flash freq (#7989)
• board manager: + Agrumino lemon v4 (#7883)
• Fix improper GENERIC board IDs (#7839)
• boards.txt: sort by displayed name (#7670)
• add sdk options to "generic esp8285 module" (#7550)

Build system

• Update board-specific defines (#7875)
• Add a check for all URLs in the package file (#7848)
• Fix typo in 32-bit Windows package JSON (#7847)
• PIO: Dynamically configure exceptions support (#7834)
• platform.txt: instruct GCC to perform more aggressive optimization (#7770)
• makecorever.py: Hide GIT error messages. Fixes #7744 (#7745)
• Normalize platform.txt pattern numbers (#7752)
• Fix platform.txt issue for Windows (#7750)
• Update to pyserial 3.5, esptool 3.0 (#7737)
• Added GZipped OTA support in elf2bin and PlatformIO (#7727)
• Use -std=gnu17 instead of -std=c17 for GCC and test (#7588)
• Compile failure fix with FS_NO_GLOBALS flag (#7685)
• Update to GCC 10.2 (#7607)
• Upgrade to GCC 10.1 toolchain (#6294)

Emulation on host

• minor host fix found while compiling arduinoJson (#8009)
• emulation on host: millis()/micros() now start at 0 (#7810)
• mock: +hexdump() from debug.cpp (#7789)
• emulation on host: makefile rework: only one build dir (#7738, #7740, #7741)
• emulation on host makefile update, allowing to pass more options (#7552)