Offline Wikipedia on ESP32-S3

Run a complete, searchable copy of Wikipedia on a low-cost ESP32-S3 board, with no internet connection required. The ESP32 hosts its own Wi-Fi access point and web server, serving articles (and images) straight from a microSD card. Connect with any phone, tablet, or laptop and browse.

This is made possible by Kiwix, a non-profit that makes free knowledge available offline through open-source ZIM archives.

Original tutorial: Circuit Digest - How to Build an Offline Wikipedia Using ESP32 Repository: https://github.com/Circuit-Digest/Offline-Wikipedia-ESP32-master

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Features

• Fully offline: no cloud, no router, no internet
• Built-in Wi-Fi access point (Wikipedia-Offline), open network
• Search bar with live article suggestions
• Full article text, with optional images and diagrams
• Works with any language or topic Kiwix provides (Wikipedia, physics, mathematics, chess, football, etc.)
• Serial Monitor remains active for diagnostics

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Hardware Required

Component	Notes
ESP32-S3 board with microSD slot	e.g. ESP32-S3 CAM module. ESP32-S3 is required as the firmware expects an ESP32-S3 board
microSD card	16 GB or 32 GB recommended. A 2-4 GB card works if the data fits
USB data cable	For flashing the firmware
PC with VS Code + PlatformIO	Used for preprocessing and flashing

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Step-by-Step Setup

Step 1: Download the correct ZIM file

Go to the Kiwix Wikipedia dump page and pick a file whose size fits your microSD card.

File names follow a pattern such as wikipedia_en-simple_all_maxi_2026-09.zim:

Tag	Meaning
en, af, ru, fr, ...	Language code (English, Afrikaans, Russian, French, etc.)
simple	Simple English Wikipedia: easier vocabulary, fewer articles, much smaller file
all	General articles across all topics, not a single subject
maxi	Full version with complete text and images
nopic	Text only, no pictures, much smaller
mini	Lead/intro paragraphs of articles only
2026-XX	Year and month the snapshot was taken

Topic-specific archives (physics, mathematics, football, chess, ...) are also available. If you don't want images, choose a nopic file.

Step 2: Clone the repository

git clone https://github.com/Circuit-Digest/Offline-Wikipedia-ESP32-master.git
cd Offline-Wikipedia-ESP32-master

All following commands are run from the root of the cloned repository (the tutorial uses VS Code with PlatformIO).

Step 3: Preprocess the ZIM file

This re-compresses the ZIM contents so the ESP32 can read them efficiently. It extracts all articles, renders images/diagrams into .dat chunks, and generates the index files.

The default thumbnail size is 320x212. The example below uses 480x320 for sharper images.

& "C:\Users\<YourUser>\.platformio\penv\Scripts\python.exe" preprocessor\build_wiki_db.py --all-jpeg --thumb-size 480x320 "C:\Users\<YourUser>\Downloads\wikipedia_en-simple_all_maxi_2026-09.zim" preprocessor\output_en_wiki

• Replace <YourUser> and the .zim path with your own.
• Processing can take a while, depending on the ZIM size.
• The output folder (output_en_wiki) can be renamed to match your language, e.g. output_af_wiki for Afrikaans.

Step 4: Copy the data to the microSD card

1. Plug the microSD card into your PC and format it as FAT32 (Windows: right-click the drive > Format > FAT32).
2. Create a folder named wiki in the root of the card.
3. Copy all files from preprocessor\output_en_wiki\ into /wiki/.

The card should look like this:

SD Card Root/
└── wiki/
    ├── index.bin
    ├── sparse_index.bin
    ├── id_index.bin
    ├── index_meta.txt
    ├── articles_0000.dat
    ├── articles_0001.dat
    ...
    ├── img_index.bin
    ├── img_meta.txt
    ├── img_0000.dat
    ├── img_0001.dat
    ...

Insert the card into the microSD slot on the ESP32-S3 board.

Step 5: Flash the web server firmware

Connect the ESP32-S3 over USB and run:

cd firmware
$env:PYTHONIOENCODING="utf-8"
& "C:\Users\<YourUser>\.platformio\penv\Scripts\pio.exe" run -e s3-cam-web -t upload

No changes are needed. A success message appears when flashing completes. If it fails, check that you are using an ESP32-S3 board, as the firmware expects one.

Step 6: Verify the boot

Open the Serial Monitor:

& "C:\Users\<YourUser>\.platformio\penv\Scripts\pio.exe" device monitor

A healthy boot looks like this (article counts vary by ZIM file):

[wiki_db] Initialising storage...
[wiki_db] Setting custom SD_MMC pins: CLK=39, CMD=38, D0=40
[wiki_db] SD_MMC mounted successfully (1-bit mode)!
[wiki_db] Database ready: 129909 articles
[wiki_db] Images: 129909 available

Step 7: Connect and browse

1. Power on the ESP32-S3.
2. On your phone, tablet, or laptop, connect to the Wi-Fi network Wikipedia-Offline (open network, no password).
3. Open a browser and go to http://192.168.4.1/

You'll see the "Welcome to Offline Wikipedia" page with the total article count. Start typing in the search bar to see matching articles, then click one to read the full content (text and images, or text only if you used a nopic file).

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Troubleshooting

Problem	Likely cause
Firmware upload fails	Board is not an ESP32-S3
SD card not mounted in Serial Monitor	Card not formatted as FAT32, or files not inside /wiki/
Not enough space on card	ZIM output is larger than the card; use simple, nopic, or mini, or a bigger card
Can't open the page	Confirm you're connected to Wikipedia-Offline and use http://192.168.4.1/

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Ideas for Extension

• Add a TFT display to read articles directly on the device instead of through a browser
• Integrate an offline text-to-speech system so articles are read aloud
• Build an emergency survival kit or off-grid educational tool

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Credits

• Kiwix for the open ZIM archives
• Circuit Digest for the original tutorial and code

License

Check the repository's license file for details. Wikipedia content is available under its own open licenses (CC BY-SA).