Serial Monitor & Flasher

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Share & Store

/p Paste /s Share /n Note (Markdown) /r Note (Rich Text) /i Image /u URL /secret Encrypted Secret /drop Local Drop /clip Clipboard Sync /hook Webhook Tester /poll Poll /survey Survey /screen Screen Share /call Video Call /board Shared Whiteboard /geoshare Live Location /my My Tools /share Share Receiver

Encode & Decode

/forge Forge /b64 Base64 / 32 / Hex /urlencode URL Encode /entities HTML Entities /escape Escape /jwt JWT /gz Gzip /zip Zip / Tar /bin Text ↔ Binary /rot ROT13 / Caesar /datauri Data URI /uni Unicode Inspector /punycode Punycode / IDN /hexdump Hex Viewer /magic Smart Decoder /charset Character Encoding /filetype File Type

Data & Config

/json JSON / YAML / TOML /jsontree JSON Tree /xml XML Studio /csv CSV ↔ JSON /xlsx Excel / XLSX /qs Query String /env .env Parser /sqllab SQL Lab /types JSON → Types /jsondiff JSON Diff /valid Validators /jtable JSON → Table /chart Chart Maker /compose Docker Compose /proxygen Proxy Config /phone Phone Parser /geojson GeoJSON Viewer /har HAR Viewer /commitlint Commit Linter /semver Semver Calculator /openapi OpenAPI / Swagger /makefile Makefile /dockerfile Dockerfile Linter /deps Vuln Scanner /jsonschema JSON Schema Validator /serialized Serialized Data

Text

/diff Diff /regex Regex Lab /case Case Converter /str String Ops /sort Sort / Filter /text Text Stats /md Markdown /post Post Formatter /slug Slugify /plain Plain Text & Invisible Characters /mdtable Markdown Table /beautify Code Formatter /lists List Comparer /htmlmd HTML → Markdown /emailhtml Email HTML Builder /jsx HTML → JSX /emailnorm Email Normalizer

Run Code

/js JS Console /py Python Console /java Java Sandbox /wasm WASM Runner

AI & Prompts

/tokens Token Counter & Visualizer /prompt Prompt Template /toolschema Tool Schema Builder /chatjson Chat Message Builder /mcpconfig MCP Config /llmstxt llms.txt /agentsmd AGENTS.md /injscan Injection Scan /abcompare A/B Compare /jsonl JSONL Viewer /mcptest MCP Tester

Agile & Scrum

/poker Planning Poker /sprint Sprint Capacity /retro Retro Formats

Crypto & Passwords

/hash Hash & Checksum /hmac HMAC /pass Password /uuid UUID / ULID /totp TOTP / 2FA Code /bip39 BIP39 Seed Phrase /pwhash Password Hash /cert Certificate Decoder /aes AES Text Encryption /age age Encryption /shamir Shamir's Secret Sharing /pwned Password Breach Check /keypair Key Pair Generator /htpasswd Basic Auth

Numbers & Math

/baseconv Base Convert /num Number Format /roman Roman Numerals /unit Unit Converter /calc Percentage Calc /prime Primes & Factors /stats Number Stats /plot Function Plotter /frac Fractions /gcd GCD & LCM /comb Combinatorics /solve Equation Solver /matrix Matrix /finance Finance /eval Math Evaluator /bit Bitwise Calculator /float Float Inspector /triangle Triangle Solver

Electronics

/ohm Ohm's Law /rescolor Resistor Colors /ledres LED Resistor /vdiv Voltage Divider /filter Filter Calculator /capcode Capacitor Code /ne555 555 Timer /rcomb Series / Parallel R-C /react Reactance /awg Wire Gauge /db Decibels /opamp Op-Amp Gain /lm317 LM317 /battery Battery Life /vdrop Voltage Drop /pcb PCB Trace Width /battpack Battery Pack /zener Zener Diode /bjt Transistor Bias /ripple PSU Ripple /fuse Fuse Selector /pwm PWM Duty /ntc Thermistor NTC /circuit Circuit Builder /kicad KiCad Viewer /serial Serial / Flasher

Radio & RF

/wavelength Wavelength /antenna Antenna Length /fspl Path Loss (FSPL) /linkbudget Link Budget /dtmf DTMF Encoder /bandplan Band Plan

IoT & Protocols

/lorawan LoRaWAN Airtime /payload Payload Size /mqtt MQTT Tree /modbus Modbus Register /mesh Meshtastic

Energy

/solar Solar Yield /batteryroi Battery ROI /tariff Tariffs /co2 Device CO₂ /evcharge EV Charging /peakload Peak Load /scop SCOP

Fabrication

/filament Filament /feeds Feeds & Speeds /lasercut Laser Cut /steps Steps/mm /stl 3D Viewer /scad SCAD /outline Photo to STL

Outdoors & Sky

/goldenhour Golden Hour /sunpos Sun Position /sunrise Sunrise / Sunset /moon Moon Phase /dewpoint Dew Point /windchill Feels Like /coords Coordinates /gpsdist GPS Distance /calories Calorie Burn /hiking Hiking Time /packing Packing List /stars Sky Map /astroplan Astro Planner /scope Telescope Setup /hunt Scavenger Hunt

Date & Time

/epoch Timestamp /tz Timezone /time Current Time /dt Date Calc /cron Cron /timer Timer / Stopwatch /snowflake ID Timestamp Decoder /datepoll Group Date Picker /workdays Business Days /eta ETA Calculator

Web & Design

/color Color /palette Palette / Contrast /gradient CSS Gradient /shadow Box Shadow /px px ↔ rem /ratio Aspect Ratio /meta Meta Tags /svg SVG Tools /favicon Favicon Maker /placeholder Placeholder Image /codeshot Code Image /cvd CVD Simulator /mermaid Mermaid Diagram /dot Graphviz DOT /font Font Inspector /bezier cubic-bezier /clamp CSS clamp() /cssjs CSS ↔ JS Object /quoteimg Quote → Image /paint Pixel Paint /meme Meme Generator /avatar Avatar Generator /pattern Pattern Generator /grid CSS Grid /glass Glassmorphism /handwrite Handwriting /illusion Optical Illusion /img2ascii Image to ASCII /blurhash BlurHash /loader CSS Loader /blob Blob & Border-Radius /robots Robots.txt Tester

Network

/x Ping /x DNS /x WHOIS /x Traceroute /x HTTP Headers /x Port Check /x Email DNS Check /x TLS / SSL Check /cidr CIDR / Subnet /ip My IP /ua User-Agent Parser /req HTTP Request Runner /mac MAC Address /secheaders Header Security /csphash CSP Hash /socket WebSocket Tester /clean URL Cleaner

Generate

/qr QR Code /lorem Lorem Ipsum /fake Fake Data /utm UTM Builder /ythumb YT Thumbnail /gitignore .gitignore /license License Text /ics Calendar Event /vcard vCard Generator /barcode Barcode Generator

Learn

/learn All explainers /learn How an LLM Works /learn How the JVM Works /learn How TypeScript Works /learn How HTTPS & TLS Work /learn How Git Works /learn How DNS Works /learn How WebRTC Works

Reference

/ascii ASCII Table /http HTTP Codes /mime MIME Types /ports Port Numbers /symbols Symbol Picker /keycode Key Event Inspector /chmod Chmod /emoji Emoji Picker /gitref Git Cheatsheet /api API & MCP /app 1234.nu Android App

Device Tests

/cam Webcam Test /mic Microphone Test /keytest Keyboard Test /mousetest Mouse Test /speaker Speaker Test /screentest Dead Pixel Test /touchtest Touchscreen Test /gamepad Gamepad Test /sensors Motion Sensors /deviceinfo Device Info /fingerprint Browser Fingerprint Self-Test /benchmark Device Benchmark /gps GPS Dashboard /lightmeter Light Meter /nfc NFC Tag

Sensors & Signals

/signal Signal Generator /lightning Lightning Distance /trigstop Trigger Stopwatch /monitor Remote Monitor /soundmeter Sound Meter /echoloc Sound Locator

Music & Audio

/tuner Instrument Tuner /metronome Metronome /notefreq Note & Frequency /delay Delay Time /capo Transpose /scales Scales & Chords /midi MIDI Inspector

Media

/img Image Convert /img Image Resize /img Image Compress /heic HEIC Converter /aud Audio Waveform /aud Audio Convert /aud Audio Trim /vid Video Convert /vid Video Compress /vid Video Trim /vid Extract Frame /vid Remove Audio /vid Change Speed /say Text to Speech /exif EXIF Viewer & Stripper /pdf PDF Tools /docmeta Document Metadata Inspector & Stripper /imgdiff Image Diff /rec Screen Recorder /ocr Image OCR /imglabel Image Labeling /stt Speech to Text /subs Subtitle Converter /imgedit Image Editor /scan QR Scanner /translate Translate /astrostack Astro Stacker /scan3d 3D Scan Capture /splat Splat Viewer

Fun

/nato Spelling Alphabet /morse Morse Code /fancy Text Styler /dice Dice Roller /banner ASCII Banner /fact Random Facts /coin Coin Flip /yesno Yes or No /asciidraw ASCII Draw /wheel Spin the Wheel /piano Piano /reaction Reaction Time /nummem Number Memory /fan Spinning Fan /fractal Fractal Explorer

Games

/play All games /play 2048 /play Minesweeper /play Word Guess /play Groups /play Snake /play Tetris /play Sudoku /play Memory Match /play Typing Test /play Connect Four /play Game of Life /play Chess /play Solitaire /play Battleship /play Breakout /play Simon /play 15 Puzzle /play Hangman /play Flappy /play Pong /play Asteroids /play Reversi /play Checkers /play Mahjong Solitaire /play Doomed /play Stunt Viper /play Voxel Strike /play Ecosystem /play Falling Sand /play Marble Roll /play Gravity /play Times Tables /play Pinball /play Sideways /play Wind-Ups /play Fluid Ink /play Horde Rush /play Neuroevolution Lab /play Bomber Arena /play 20 Questions /play Wander /play Star Battle

Dutch Tax & Money

/salaris Salary /btw BTW Calculator /box3 Box 3 /zzp ZZP Net /expat 30% Ruling /employercost Employer Cost /hypotheek Mortgage /kostenkoper Buying Costs /hra HRA /toeslagen Toeslagen /transitievergoeding Transitievergoeding /aow AOW /studieschuld Student Debt /inflatie Inflation

Money & Finance

/invest Investing /fire FIRE Calculator /split Bill Split

Health & Body

/bmi Body Metrics

← Electronics 🔒 Runs in your browser

/serial — Serial Monitor & Flasher

A browser serial terminal and an ESP firmware flasher — talk to any Arduino, ESP32/ESP8266 or USB-serial board, and flash Espressif chips, straight from this tab. Uses the Web Serial API; nothing is uploaded or installed.

Your browser doesn't support the Web Serial API. Use a Chromium-based browser on desktop — Chrome, Edge or Opera — over HTTPS (or localhost). Firefox and Safari don't expose serial ports.

This tool needs a desktop computer. The Web Serial API it relies on doesn't exist on any phone or tablet browser, and it isn't available inside the 1234.nu app either — there's no mobile version of this feature. Open this page on a desktop computer instead, using Chrome, Edge or Opera.

disconnected baud

Port settings

data bits parity stop bits flow control

timestamps hex view autoscroll local echo

Signals DTR RTS 0 B in · 0 B out · 0 lines

Flashes Espressif chips — ESP8266, ESP32, and the ESP32-S2/S3/C3/C6/H2 family — using Espressif's own esptool engine. Put the board in download mode if it doesn't enter it automatically (hold BOOT/GPIO0, tap EN/RST, release). AVR Arduinos (Uno/Nano) can be monitored on the other tab; flashing them is not yet supported here.

disconnected flash baud

Chip—

MAC—

Features—

Flash ID—

Offsets are hex. Single combined image → 0x0. ESP32 app partition → 0x10000.

erase entire flash first compress while writing reset to run after flashing

1234.nu · no accounts, no tracking · about · privacy · android app · theme · app settings · powered by esptool-js · build 1157 (631a0585) · buy me a kroket

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Attaches your screen size, viewport, aspect ratio, browser, language, theme and the site build version, plus any errors the page logged while you were here. No tracking, no IP, no profile, but this and your message do reach us, so don't include anything private. We only need it to reproduce bugs that show up on some devices but not others, or to read the error behind a tool that "does nothing". Reports are kept only as long as needed and then deleted (see privacy). Uncheck to send just your message.

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How this works

Stores only this report's id in your browser (localStorage) so a small note can pop up here once it ships. No account, nothing sent to us, no tracking. Clearing this site's data forgets it.

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