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+Configuration files
+---
+
+There are some configs you need to change in the files below
+
+```
+./config.json      ----application settings
+```
+
+> Note: Environment variables will overwrite config setting. Please refer [Environment Variables](Environment-Variables) to get more information about environment variables.
+
+Application settings `config.json`
+---
+
+| variables | example values | description |
+| --------- | ------ | ----------- |
+| debug | `true` or `false` | set debug mode, show more logs |
+| domain | `localhost` | domain name |
+| urlpath | `hackmd` | sub url path, like `www.example.com/<urlpath>` |
+| port | `80` | web app port |
+| alloworigin | `['localhost']` | domain name whitelist |
+| usessl | `true` or `false` | set to use ssl server (if true will auto turn on `protocolusessl`) |
+| protocolusessl | `true` or `false` | set to use ssl protocol for resources path (only applied when domain is set) |
+| urladdport | `true` or `false` | set to add port on callback url (port 80 or 443 won't applied) (only applied when domain is set) |
+| usecdn | `true` or `false` | set to use CDN resources or not (default is `true`) |
+| allowanonymous | `true` or `false` | set to allow anonymous usage (default is `true`) |
+| allowfreeurl | `true` or `false` | set to allow new note by accessing not exist note url |
+| defaultpermission | `freely`, `editable`, `limited`, `locked` or `private` | set notes default permission (only applied on signed users) |
+| dburl | `mysql://localhost:3306/database` | set the db url, if set this variable then below db config won't be applied |
+| db | `{ "dialect": "sqlite", "storage": "./db.hackmd.sqlite" }` | set the db configs, [see more here](http://sequelize.readthedocs.org/en/latest/api/sequelize/) |
+| sslkeypath | `./cert/client.key` | ssl key path (only need when you set usessl) |
+| sslcertpath | `./cert/hackmd_io.crt` | ssl cert path (only need when you set usessl) |
+| sslcapath | `['./cert/COMODORSAAddTrustCA.crt']` | ssl ca chain (only need when you set usessl) |
+| dhparampath | `./cert/dhparam.pem` | ssl dhparam path (only need when you set usessl) |
+| tmppath | `./tmp/` | temp directory path |
+| defaultnotepath | `./public/default.md` | default note file path |
+| docspath | `./public/docs` | docs directory path |
+| indexpath | `./public/views/index.ejs` | index template file path |
+| hackmdpath | `./public/views/hackmd.ejs` | hackmd template file path |
+| errorpath | `./public/views/error.ejs` | error template file path |
+| prettypath | `./public/views/pretty.ejs` | pretty template file path |
+| slidepath | `./public/views/slide.hbs` | slide template file path |
+| sessionname | `connect.sid` | cookie session name |
+| sessionsecret | `secret` | cookie session secret |
+| sessionlife | `14 * 24 * 60 * 60 * 1000` | cookie session life |
+| staticcachetime | `1 * 24 * 60 * 60 * 1000` | static file cache time |
+| heartbeatinterval | `5000` | socket.io heartbeat interval |
+| heartbeattimeout | `10000` | socket.io heartbeat timeout |
+| documentmaxlength | `100000` | note max length |
+| email | `true` or `false` | set to allow email signin |
+| allowemailregister  | `true` or `false` | set to allow email register (only applied when email is set, default is `true`) |
+| imageUploadType | `imgur`(default), `s3` or `filesystem` | Where to upload image
+| s3 | `{ "accessKeyId": "YOUR_S3_ACCESS_KEY_ID", "secretAccessKey": "YOUR_S3_ACCESS_KEY", "region": "YOUR_S3_REGION", "bucket": "YOUR_S3_BUCKET_NAME" }` | When `imageUploadType` be setted to `s3`, you would also need to setup this key, check our [S3 Image Upload Guide](docs/guides/s3-image-upload.md) |
+
+Third-party integration api key settings
+---
+
+| service | settings location | description |
+| ------- | --------- | ----------- |
+| facebook, twitter, github, gitlab, dropbox, google, ldap | environment variables or `config.json` | for signin |
+| imgur | environment variables or `config.json` | for image upload |
+| google drive(`google/apiKey`, `google/clientID`), dropbox(`dropbox/appKey`) | `config.json` | for export and import |
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