diff --git a/app/client/components/UnsavedChanges.ts b/app/client/components/UnsavedChanges.ts
new file mode 100644
index 00000000..5d0c3177
--- /dev/null
+++ b/app/client/components/UnsavedChanges.ts
@@ -0,0 +1,48 @@
+/**
+ * Module to help deal with unsaved changes when closing a page.
+ */
+import {Disposable} from 'grainjs';
+
+/**
+ * Create an UnsavedChanges object to indicate there are UnsavedChanges. Dispose it when this is
+ * no longer the case. The optional callback will be called to confirm there are indeed unsaved
+ * changes. If omitted, it is assumed that there are.
+ */
+export class UnsavedChange extends Disposable {
+  constructor(
+    // If given, saveChanges() will call it to save changes.
+    private _saveCB?: () => Promise<void>,
+    // If given, it may return false to indicate that actually nothing has changed.
+    private _haveChanges?: () => boolean,
+  ) {
+    super();
+    unsavedChanges.add(this);
+    this.onDispose(() => unsavedChanges.delete(this));
+  }
+  public haveUnsavedChanges() { return !this._haveChanges || this._haveChanges(); }
+  public async save(): Promise<void> { return this._saveCB && this._saveCB(); }
+}
+
+export class UnsavedChangeSet {
+  private _changes = new Set<UnsavedChange>();
+
+  /**
+   * Check if there are any unsaved changes out there.
+   */
+  public haveUnsavedChanges(): boolean {
+    return Array.from(this._changes).some((c) => c.haveUnsavedChanges());
+  }
+
+  /**
+   * Save any unsaved changes out there.
+   */
+  public async saveChanges(): Promise<void> {
+    await Promise.all(Array.from(this._changes).map((c) => c.save()));
+  }
+
+  public add(unsaved: UnsavedChange) { this._changes.add(unsaved); }
+  public delete(unsaved: UnsavedChange) { this._changes.delete(unsaved); }
+}
+
+// Global set of UnsavedChanges, checked on page unload.
+export const unsavedChanges = new UnsavedChangeSet();
diff --git a/app/client/lib/UrlState.ts b/app/client/lib/UrlState.ts
new file mode 100644
index 00000000..faddb088
--- /dev/null
+++ b/app/client/lib/UrlState.ts
@@ -0,0 +1,140 @@
+/**
+ * Generic support of observable state represented by the current page's URL. The state is
+ * initialized on first use, and updated on navigation events, such as Back/Forward button clicks,
+ * and on calls to pushUrl().
+ *
+ * Application-specific module should instantiate UrlState with the desired way to encode state in
+ * URLs. Other code may then use the UrlState object exposed by that app-specific module.
+ *
+ * UrlState also provides functions to navigate: makeUrl(), pushUrl(), and setLinkUrl(). The
+ * preferred option is to use actual <a> links for navigation, creating them like so:
+ *
+ *    import {urlState} from '...appUrlState';
+ *    dom('a', urlState().setLinkUrl({org: 'foo'}))
+ *    dom('a', urlState().setLinkUrl({docPage: pageId}))
+ *
+ * These will set actual hrefs (e.g. allowing links to be opened in a new tab), and also will
+ * intercept clicks and update history (using pushUrl()) without reloading the page.
+ */
+import * as log from 'app/client/lib/log';
+import {BaseObservable, Disposable, dom, DomElementMethod, observable} from 'grainjs';
+
+export interface UrlStateSpec<IUrlState> {
+  encodeUrl(state: IUrlState, baseLocation: Location | URL): string;
+  decodeUrl(location: Location | URL): IUrlState;
+  updateState(prevState: IUrlState, newState: IUrlState): IUrlState;
+
+  // If present, the return value is checked by pushUrl() to decide if we can stay on the page or
+  // need to load the new URL. The new URL is always loaded if origin changes.
+  needPageLoad(prevState: IUrlState, newState: IUrlState): boolean;
+
+  // Give the implementation a chance to complete outstanding work, e.g. if there is unsaved
+  // data in the page state that would get destroyed.
+  delayPushUrl(prevState: IUrlState, newState: IUrlState): Promise<void>;
+}
+
+/**
+ * Represents the state of a page in browser history, as encoded in window.location URL.
+ */
+export class UrlState<IUrlState> extends Disposable {
+  // Current state. This gets initialized in the constructor, and updated on navigation events.
+  public state = observable<IUrlState>(this._getState());
+
+  constructor(private _window: HistWindow, private _stateImpl: UrlStateSpec<IUrlState>) {
+    super();
+
+    // Create a hook for navigation. It's exposed on the window for overriding in tests.
+    if (!_window._urlStateLoadPage) {
+      _window._urlStateLoadPage = (href) => { _window.location.href = href; };
+    }
+
+    // On navigation events, update our current state, including the observables.
+    this.autoDispose(dom.onElem(this._window, 'popstate', (ev) => this.loadState()));
+  }
+
+  /**
+   * Creates a new history entry (navigable with Back/Forward buttons), encoding the given state
+   * in the URL. This is similar to navigating to a new URL, but does not reload the page.
+   */
+  public async pushUrl(urlState: IUrlState, options: {replace?: boolean, avoidReload?: boolean} = {}) {
+    const prevState = this.state.get();
+    const newState = this._stateImpl.updateState(prevState, urlState);
+    const newUrl = this._stateImpl.encodeUrl(newState, this._window.location);
+
+    // Don't create a new history entry if nothing changed as it would only be annoying.
+    if (newUrl === this._window.location.href) { return; }
+
+    const oldOrigin = this._window.location.origin;
+    const newOrigin = new URL(newUrl).origin;
+
+    // We can only pushState() without reloading the page if going to a same-origin URL.
+    const samePage = (oldOrigin === newOrigin &&
+      (options.avoidReload || !this._stateImpl.needPageLoad(prevState, newState)));
+
+    if (samePage) {
+      await this._stateImpl.delayPushUrl(prevState, newState);
+      if (options.replace) {
+        this._window.history.replaceState(null, '', newUrl);
+      } else {
+        this._window.history.pushState(null, '', newUrl);
+      }
+      // pushState/replaceState above do not trigger 'popstate' event, so we call loadState() manually.
+      this.loadState();
+    } else {
+      this._window._urlStateLoadPage!(newUrl);
+    }
+  }
+
+  /**
+   * Creates a URL (e.g. to use in a link's href) encoding the given state. The `use` argument
+   * allows for this to be used in a computed, and is used by setLinkUrl().
+   */
+  public makeUrl(urlState: IUrlState, use: UseCB = unwrap): string {
+    const fullState = this._stateImpl.updateState(use(this.state), urlState);
+    return this._stateImpl.encodeUrl(fullState, this._window.location);
+  }
+
+  /**
+   * Applies to an <a> element to create a smart link, e.g. dom('a', setLinkUrl({ws: wsId})). It
+   * both sets the href (e.g. to allow the link to be opened to a new tab), AND intercepts plain
+   * clicks on it to "follow" the link without reloading the page.
+   */
+  public setLinkUrl(urlState: IUrlState): DomElementMethod[] {
+    return [
+      dom.attr('href', (use) => this.makeUrl(urlState, use)),
+      dom.on('click', (ev) => {
+        // Only override plain-vanilla clicks.
+        if (ev.shiftKey || ev.metaKey || ev.ctrlKey || ev.altKey) { return; }
+        ev.preventDefault();
+        return this.pushUrl(urlState);
+      }),
+    ];
+  }
+
+  /**
+   * Reset the state from the current URL. This shouldn't normally need to get called. It's called
+   * automatically when needed. It's also used by tests.
+   */
+  public loadState() {
+    log.debug(`loadState ${this._window.location.href}`);
+    this.state.set(this._getState());
+  }
+
+  private _getState(): IUrlState {
+    return this._stateImpl.decodeUrl(this._window.location);
+  }
+}
+
+// This is what we expect from the global Window object. Tests may override with a mock.
+export interface HistWindow extends EventTarget {
+  history: History;
+  location: Location;
+
+  // This is a hook we create, to allow stubbing or overriding in tests.
+  _urlStateLoadPage?: (href: string) => void;
+}
+
+// The type of a 'use' callback as used in a computed(). It's what makes a computed subscribe to
+// its dependencies. The unwrap() helper allows using a dependency without any subscribing.
+type UseCB = <T>(obs: BaseObservable<T>) => T;
+const unwrap: UseCB = (obs) => obs.get();
diff --git a/app/client/lib/log.ts b/app/client/lib/log.ts
new file mode 100644
index 00000000..4aa6418f
--- /dev/null
+++ b/app/client/lib/log.ts
@@ -0,0 +1,15 @@
+/**
+ * Client-side debug logging.
+ * At the moment this simply logs to the browser console, but it's still useful to have dedicated
+ * methods to allow collecting them in the future, or silencing them in production or in mocha
+ * tests.
+ */
+
+export type LogMethod = (message: string, ...args: any[]) => void;
+
+// tslint:disable:no-console
+export const debug: LogMethod = console.debug.bind(console);
+export const info: LogMethod = console.info.bind(console);
+export const log: LogMethod = console.log.bind(console);
+export const warn: LogMethod = console.warn.bind(console);
+export const error: LogMethod = console.error.bind(console);
diff --git a/app/client/models/gristUrlState.ts b/app/client/models/gristUrlState.ts
new file mode 100644
index 00000000..d3c18be2
--- /dev/null
+++ b/app/client/models/gristUrlState.ts
@@ -0,0 +1,160 @@
+/**
+ * This module provides a urlState() function returning a singleton UrlState, which represents
+ * Grist application state as encoded into a URL, and navigation functions.
+ *
+ * For example, the current org is available as a value or as an observable:
+ *
+ *    urlState().state.get().org
+ *    computed((use) => use(urlState().state).org);
+ *
+ * Creating a link which has an href but changes state without reloading page is possible with:
+ *
+ *    dom('a', urlState().setLinkUrl({ws: 10}), "...")
+ *
+ * Grist URLs have the form:
+ *    <org-base>/
+ *    <org-base>/ws/<ws>/
+ *    <org-base>/doc/<doc>[/p/<docPage>]
+ *
+ * where <org-base> depends on whether subdomains are in use, i.e. one of:
+ *    <org>.getgrist.com
+ *    localhost:8080/o/<org>
+ *
+ * Note that the form of URLs depends on the settings in window.gristConfig object.
+ */
+import {unsavedChanges} from 'app/client/components/UnsavedChanges';
+import {UrlState} from 'app/client/lib/UrlState';
+import {decodeUrl, encodeUrl, getSlugIfNeeded, GristLoadConfig, IGristUrlState, useNewUI} from 'app/common/gristUrls';
+import {Document} from 'app/common/UserAPI';
+import isEmpty = require('lodash/isEmpty');
+
+/**
+ * Returns a singleton UrlState object, initializing it on first use.
+ */
+export function urlState(): UrlState<IGristUrlState> {
+  return _urlState || (_urlState = new UrlState(window, new UrlStateImpl(window as any)));
+}
+let _urlState: UrlState<IGristUrlState>|undefined;
+
+// Returns url parameters appropriate for the specified document, specifically `doc` and `slug`.
+export function docUrl(doc: Document): IGristUrlState {
+  return {doc: doc.urlId || doc.id, slug: getSlugIfNeeded(doc)};
+}
+
+// Returns the home page for the current org.
+export function getMainOrgUrl(): string { return urlState().makeUrl({}); }
+
+// Get url for the login page, which will then redirect to nextUrl (current page by default).
+export function getLoginUrl(nextUrl: string = _getCurrentUrl()): string {
+  return _getLoginLogoutUrl('login', nextUrl);
+}
+
+// Get url for the logout page, which will then redirect to nextUrl (signed-out page by default).
+export function getLogoutUrl(nextUrl: string = getSignedOutUrl()): string {
+  return _getLoginLogoutUrl('logout', nextUrl);
+}
+
+// Get url for the login page, which will then redirect to nextUrl (current page by default).
+export function getLoginOrSignupUrl(nextUrl: string = _getCurrentUrl()): string {
+  return _getLoginLogoutUrl('signin', nextUrl);
+}
+
+// Get url for the reset password page.
+export function getResetPwdUrl(): string {
+  const startUrl = new URL(window.location.href);
+  startUrl.pathname = '/resetPassword';
+  return startUrl.href;
+}
+
+// Returns the URL for the "you are signed out" page.
+export function getSignedOutUrl(): string { return getMainOrgUrl() + "signed-out"; }
+
+// Helper which returns the URL of the current page, except when it's the "/signed-out" page, in
+// which case returns the org URL. This is a good URL to use for a post-login redirect.
+function _getCurrentUrl(): string {
+  return window.location.pathname.endsWith("/signed-out") ? getMainOrgUrl() : window.location.href;
+}
+
+// Helper for getLoginUrl()/getLogoutUrl().
+function _getLoginLogoutUrl(method: 'login'|'logout'|'signin', nextUrl: string): string {
+  const startUrl = new URL(window.location.href);
+  startUrl.pathname = '/' + method;
+  startUrl.searchParams.set('next', nextUrl);
+  return startUrl.href;
+}
+
+export type IDocPage = number | 'new' | 'code';
+
+/**
+ * Implements the interface expected by UrlState. It is only exported for the sake of tests; the
+ * only public interface is the urlState() accessor.
+ */
+export class UrlStateImpl {
+  constructor(private window: {gristConfig?: Partial<GristLoadConfig>}) {}
+
+  /**
+   * The actual serialization of a url state into a URL. The URL has the form
+   *    <org-base>/
+   *    <org-base>/ws/<ws>/
+   *    <org-base>/doc/<doc>[/p/<docPage>]
+   *    <org-base>/doc/<doc>[/m/fork][/p/<docPage>]
+   *
+   * where <org-base> depends on whether subdomains are in use, e.g.
+   *    <org>.getgrist.com
+   *    localhost:8080/o/<org>
+   */
+  public encodeUrl(state: IGristUrlState, baseLocation: Location | URL): string {
+    const gristConfig = this.window.gristConfig || {};
+    return encodeUrl(gristConfig, state, baseLocation);
+  }
+
+  /**
+   * Parse a URL location into an IGristUrlState object. See encodeUrl() documentation.
+   */
+  public decodeUrl(location: Location | URL): IGristUrlState {
+    const gristConfig = this.window.gristConfig || {};
+    return decodeUrl(gristConfig, location);
+  }
+
+  /**
+   * Updates existing state with new state, with attention to Grist-specific meanings.
+   * E.g. setting 'docPage' will reuse previous 'doc', but setting 'org' or 'ws' will ignore it.
+   */
+  public updateState(prevState: IGristUrlState, newState: IGristUrlState): IGristUrlState {
+    const keepState = (newState.org || newState.ws || newState.homePage || newState.doc || isEmpty(newState) ||
+                       newState.billing || newState.welcome) ?
+      (prevState.org ? {org: prevState.org, newui: prevState.newui} : {}) :
+      prevState;
+    return {...keepState, ...newState};
+  }
+
+  /**
+   * Billing pages and doc-specific pages for now require a page load.
+   * TODO: Make it so doc pages do NOT require a page load, since we are actually serving the same
+   * single-page app for home and for docs, and should only need a reload triggered if it's
+   * a matter of DocWorker requiring a different version (e.g. /v/OTHER/doc/...).
+   */
+  public needPageLoad(prevState: IGristUrlState, newState: IGristUrlState): boolean {
+    const gristConfig = this.window.gristConfig || {};
+    const orgReload = prevState.org !== newState.org;
+    // Reload when moving to/from a document or between doc and non-doc.
+    const docReload = prevState.doc !== newState.doc;
+    // Reload when moving to/from a billing page.
+    const billingReload = Boolean(prevState.billing) !== Boolean(newState.billing);
+    // Reload when changing 'newui' flag.
+    const newuiReload = useNewUI(prevState.newui) !== useNewUI(newState.newui);
+    // Reload when moving to/from a welcome page.
+    const welcomeReload = Boolean(prevState.welcome) !== Boolean(newState.welcome);
+    return Boolean(orgReload || billingReload || gristConfig.errPage || docReload || newuiReload || welcomeReload);
+  }
+
+  /**
+   * Complete outstanding work before changes that would destroy page state, e.g. if there are
+   * edits to be saved.
+   */
+  public async delayPushUrl(prevState: IGristUrlState, newState: IGristUrlState): Promise<void> {
+    if (newState.docPage !== prevState.docPage) {
+      return unsavedChanges.saveChanges();
+    }
+  }
+}
diff --git a/app/client/ui/PagePanels.ts b/app/client/ui/PagePanels.ts
index b45bef8d..191be2a4 100644
--- a/app/client/ui/PagePanels.ts
+++ b/app/client/ui/PagePanels.ts
@@ -63,6 +63,7 @@ export function pagePanels(page: PageContents) {
 
     cssMainPane(
       cssTopHeader(
+        testId('top-header'),
         (left.hideOpener ? null :
           cssPanelOpener('PanelRight', cssPanelOpener.cls('-open', left.panelOpen),
             testId('left-opener'),
@@ -144,6 +145,9 @@ export const cssLeftPane = styled(cssVBox, `
       display: none;
     }
   }
+  .interface-light & {
+    display: none;
+  }
 `);
 const cssMainPane = styled(cssVBox, `
   position: relative;
@@ -170,6 +174,9 @@ const cssRightPane = styled(cssVBox, `
       display: none;
     }
   }
+  .interface-light & {
+    display: none;
+  }
 `);
 const cssTopHeader = styled('div', `
   height: 48px;
@@ -184,6 +191,10 @@ const cssTopHeader = styled('div', `
       display: none;
     }
   }
+
+  .interface-light & {
+    display: none;
+  }
 `);
 const cssResizeFlexVHandle = styled(resizeFlexVHandle, `
   --resize-handle-color: ${colors.mediumGrey};
diff --git a/app/client/ui2018/cssVars.ts b/app/client/ui2018/cssVars.ts
index f5f73b36..f3303d68 100644
--- a/app/client/ui2018/cssVars.ts
+++ b/app/client/ui2018/cssVars.ts
@@ -6,6 +6,7 @@
  *  https://css-tricks.com/snippets/css/system-font-stack/
  *
  */
+import {urlState} from 'app/client/models/gristUrlState';
 import {getTheme, ProductFlavor} from 'app/client/ui/CustomThemes';
 import {dom, makeTestId, styled, TestId} from 'grainjs';
 import values = require('lodash/values');
@@ -164,4 +165,6 @@ export function attachCssRootVars(productFlavor: ProductFlavor, varsOnly: boolea
   if (theme.bodyClassName) {
     document.body.classList.add(theme.bodyClassName);
   }
+  const interfaceStyle = urlState().state.get().params?.style || 'full';
+  document.body.classList.add(`interface-${interfaceStyle}`);
 }
diff --git a/app/common/DocListAPI.ts b/app/common/DocListAPI.ts
index 3fb0638d..2d5c2816 100644
--- a/app/common/DocListAPI.ts
+++ b/app/common/DocListAPI.ts
@@ -8,8 +8,9 @@ export type DocEntryTag = ''|'sample'|'invite'|'shared';
 
 export const OpenDocMode = StringUnion(
   'default',  // open doc with user's maximal access level
-  'fork',     // open doc limited to view access (if user has at least that level of access)
-  'view'     // as for 'view', but suggest a fork on any attempt to edit
+  'view',     // open doc limited to view access (if user has at least that level of access)
+  'fork',     // as for 'view', but suggest a fork on any attempt to edit - the client will
+              // enable the editing UI experience and trigger a fork on any edit.
 );
 export type OpenDocMode = typeof OpenDocMode.type;
 
diff --git a/app/common/gristUrls.ts b/app/common/gristUrls.ts
index 760c7b0a..5aa7ce09 100644
--- a/app/common/gristUrls.ts
+++ b/app/common/gristUrls.ts
@@ -1,6 +1,6 @@
 import {BillingPage, BillingSubPage, BillingTask} from 'app/common/BillingAPI';
 import {OpenDocMode} from 'app/common/DocListAPI';
-import {encodeQueryParams} from 'app/common/gutil';
+import {encodeQueryParams, isAffirmative} from 'app/common/gutil';
 import {localhostRegex} from 'app/common/LoginState';
 import {Document} from 'app/common/UserAPI';
 import identity = require('lodash/identity');
@@ -17,6 +17,10 @@ export type IHomePage = typeof HomePage.type;
 export const WelcomePage = StringUnion('user', 'teams');
 export type WelcomePage = typeof WelcomePage.type;
 
+// Overall UI style.  "full" is normal, "light" is a single page focused, panels hidden experience.
+export const InterfaceStyle = StringUnion('light', 'full');
+export type InterfaceStyle = typeof InterfaceStyle.type;
+
 // Default subdomain for home api service if not otherwise specified.
 export const DEFAULT_HOME_SUBDOMAIN = 'api';
 
@@ -59,6 +63,8 @@ export interface IGristUrlState {
   params?: {
     billingPlan?: string;
     billingTask?: BillingTask;
+    embed?: boolean;
+    style?: InterfaceStyle;
   };
   hash?: HashLink;   // if present, this specifies an individual row within a section of a page.
 }
@@ -240,6 +246,16 @@ export function decodeUrl(gristConfig: Partial<GristLoadConfig>, location: Locat
   if (sp.has('billingTask')) {
     state.params!.billingTask = parseBillingTask(sp.get('billingTask')!);
   }
+  if (sp.has('style')) {
+    state.params!.style = parseInterfaceStyle(sp.get('style')!);
+  }
+  if (sp.has('embed')) {
+    const embed = state.params!.embed = isAffirmative(sp.get('embed'));
+    // Turn view mode on if no mode has been specified.
+    if (embed && !state.mode) { state.mode = 'view'; }
+    // Turn on light style if no style has been specified.
+    if (embed && !state.params!.style) { state.params!.style = 'light'; }
+  }
   if (location.hash) {
     const hash = location.hash;
     const hashParts = hash.split('.');
@@ -301,6 +317,13 @@ function parseWelcomePage(p: string): WelcomePage {
   return WelcomePage.guard(p) ? p : 'user';
 }
 
+/**
+ * Read interface style and make sure it is either valid or left undefined.
+ */
+function parseInterfaceStyle(t: string): InterfaceStyle|undefined {
+  return InterfaceStyle.guard(t) ? t : undefined;
+}
+
 /**
  * Parses the URL like "foo.bar.baz" into the pair {org: "foo", base: ".bar.baz"}.
  * Port is allowed and included into base.
diff --git a/app/common/gutil.ts b/app/common/gutil.ts
index 089d132a..22bef03f 100644
--- a/app/common/gutil.ts
+++ b/app/common/gutil.ts
@@ -780,3 +780,12 @@ export async function isLongerThan(promise: Promise<any>, timeoutMsec: number):
   ]);
   return isPending;
 }
+
+/**
+ * Returns true if the parameter, when rendered as a string, matches
+ * 1, on, or true (case insensitively).  Useful for processing query
+ * parameters that may have been manually set.
+ */
+export function isAffirmative(parameter: any): boolean {
+  return ['1', 'on', 'true', 'yes'].includes(String(parameter).toLowerCase());
+}
diff --git a/app/server/lib/requestUtils.ts b/app/server/lib/requestUtils.ts
index 319521b0..79cb2e80 100644
--- a/app/server/lib/requestUtils.ts
+++ b/app/server/lib/requestUtils.ts
@@ -1,5 +1,6 @@
 import {ApiError} from 'app/common/ApiError';
 import {DEFAULT_HOME_SUBDOMAIN, parseSubdomain} from 'app/common/gristUrls';
+import * as gutil from 'app/common/gutil';
 import {DocScope, QueryResult, Scope} from 'app/gen-server/lib/HomeDBManager';
 import {getUserId, RequestWithLogin} from 'app/server/lib/Authorizer';
 import {RequestWithOrg} from 'app/server/lib/extractOrg';
@@ -84,7 +85,7 @@ export function allowHost(req: Request, allowedHost: string|URL) {
 }
 
 export function isParameterOn(parameter: any): boolean {
-  return ['1', 'on', 'true'].includes(String(parameter).toLowerCase());
+  return gutil.isAffirmative(parameter);
 }
 
 /**