It's there, but you're not finding it. Try inserting your fix at the bottom, as that should override the earlier appearance. Or post the full content of your prefs file here.

Hi David, many thanks for taking time out to help. I tried adding at bottom of file then saving, but no change,,:-( These are the contents of file

1. Mozilla User Preferences

/* Do not edit this file.

*
* If you make changes to this file while the application is running,
* the changes will be overwritten when the application exits.
*
* To make a manual change to preferences, you can visit the URL about:config
*/

user_pref("accessibility.lastLoadDate", 1533131890); user_pref("app.update.auto", false); user_pref("app.update.enabled", false); user_pref("app.update.lastUpdateTime.addon-background-update-timer", 1545406527); user_pref("app.update.lastUpdateTime.background-update-timer", 1545406287); user_pref("app.update.lastUpdateTime.blocklist-background-update-timer", 1545406647); user_pref("app.update.lastUpdateTime.search-engine-update-timer", 1545406167); user_pref("app.update.lastUpdateTime.xpi-signature-verification", 1545406407); user_pref("app.update.migrated.updateDir", true); user_pref("browser.cache.disk.capacity", 358400); user_pref("browser.cache.disk.filesystem_reported", 1); user_pref("browser.cache.disk.smart_size.first_run", false); user_pref("browser.cache.disk.smart_size.use_old_max", false); user_pref("browser.cache.disk.smart_size_cached_value", 358400); user_pref("browser.display.foreground_color", "#000066"); user_pref("browser.download.importedFromSqlite", true); user_pref("browser.search.countryCode", "ES"); user_pref("browser.search.region", "ES"); user_pref("calendar.list.sortOrder", "d64845d2-fd4d-4128-8e50-54e9490b5b6e"); user_pref("calendar.registry.d64845d2-fd4d-4128-8e50-54e9490b5b6e.calendar-main-default", true); user_pref("calendar.registry.d64845d2-fd4d-4128-8e50-54e9490b5b6e.calendar-main-in-composite", true); user_pref("calendar.registry.d64845d2-fd4d-4128-8e50-54e9490b5b6e.name", "Home"); user_pref("calendar.registry.d64845d2-fd4d-4128-8e50-54e9490b5b6e.type", "storage"); user_pref("calendar.registry.d64845d2-fd4d-4128-8e50-54e9490b5b6e.uri", "moz-storage-calendar://"); user_pref("calendar.timezone.local", "Europe/Paris"); user_pref("calendar.ui.version", 3); user_pref("datareporting.sessions.current.activeTicks", 84); user_pref("datareporting.sessions.current.firstPaint", 31873); user_pref("datareporting.sessions.current.main", 2977); user_pref("datareporting.sessions.current.startTime", "1545226259952"); user_pref("datareporting.sessions.current.totalTime", 180597); user_pref("datareporting.sessions.currentIndex", 44); user_pref("datareporting.sessions.prunedIndex", 43); user_pref("editor.history_title_0", ""); user_pref("editor.history_title_1", ""); user_pref("editor.history_type_0", "html"); user_pref("editor.history_type_1", "html"); user_pref("editor.history_url_0", "file:///C:/Users/ITR/Documents/My%20Web%20Sites/SignatureJetnet.html"); user_pref("editor.history_url_1", "file:///C:/Users/ITR/Documents/My%20Web%20Sites/SignatureJetnet.htm"); user_pref("editor.lastFileLocation.htmlmail", "C:\\Users\\ITR\\Documents\\My Web Sites"); user_pref("editor.lastFileLocation.image", "C:\\Users\\ITR\\Downloads"); user_pref("extensions.blocklist.pingCountTotal", 123); user_pref("extensions.blocklist.pingCountVersion", 104); user_pref("extensions.bootstrappedAddons", "{}"); user_pref("extensions.databaseSchema", 19); user_pref("extensions.e10s.rollout.hasAddon", false); user_pref("extensions.e10sBlockedByAddons", true); user_pref("extensions.enabledAddons", "ck%40everygain.com:1.4.9.8,%7B3ed8cc52-86fc-4613-9026-c1ef969da4c3%7D:3.2.4.1,%7Be2fda1a4-762b-4020-b5ad-a41df1933103%7D:5.4.8,%7B972ce4c6-7e08-4474-a285-3208198ce6fd%7D:52.8.0"); user_pref("extensions.installedDistroAddon.{e2fda1a4-762b-4020-b5ad-a41df1933103}", true); user_pref("extensions.lastAppVersion", "52.8.0"); user_pref("extensions.lastPlatformVersion", "52.8.0"); user_pref("extensions.pendingOperations", false); user_pref("extensions.shownSelectionUI", true); user_pref("extensions.translator._version", "1.0"); user_pref("extensions.ui.dictionary.hidden", true); user_pref("extensions.ui.lastCategory", "addons://list/extension"); user_pref("extensions.ui.locale.hidden", true); user_pref("extensions.update.enabled", false); user_pref("extensions.xpiState", "{\"app-profile\":{\"ck@everygain.com\":{\"d\":\"C:\\\\Users\\\\ITR\\\\AppData\\\\Roaming\\\\Thunderbird\\\\Profiles\\\\iclwyoxm.default\\\\extensions\\\\ck@everygain.com.xpi\",\"e\":true,\"v\":\"1.4.9.8\",\"st\":1391075560180},\"{3ed8cc52-86fc-4613-9026-c1ef969da4c3}\":{\"d\":\"C:\\\\Users\\\\ITR\\\\AppData\\\\Roaming\\\\Thunderbird\\\\Profiles\\\\iclwyoxm.default\\\\extensions\\\\{3ed8cc52-86fc-4613-9026-c1ef969da4c3}.xpi\",\"e\":true,\"v\":\"3.2.4.1\",\"st\":1453120945963},\"{e2fda1a4-762b-4020-b5ad-a41df1933103}\":{\"d\":\"C:\\\\Users\\\\ITR\\\\AppData\\\\Roaming\\\\Thunderbird\\\\Profiles\\\\iclwyoxm.default\\\\extensions\\\\{e2fda1a4-762b-4020-b5ad-a41df1933103}\",\"e\":true,\"v\":\"5.4.8\",\"st\":1529142666838,\"mt\":1529142664790}},\"app-global\":{\"{972ce4c6-7e08-4474-a285-3208198ce6fd}\":{\"d\":\"C:\\\\Program Files (x86)\\\\Mozilla Thunderbird\\\\extensions\\\\{972ce4c6-7e08-4474-a285-3208198ce6fd}.xpi\",\"e\":true,\"v\":\"52.8.0\",\"st\":1526529539848}}}"); user_pref("font.internaluseonly.changed", false); user_pref("font.name.monospace.el", "Consolas"); user_pref("font.name.monospace.tr", "Consolas"); user_pref("font.name.monospace.x-baltic", "Consolas"); user_pref("font.name.monospace.x-central-euro", "Consolas"); user_pref("font.name.monospace.x-cyrillic", "Consolas"); user_pref("font.name.monospace.x-unicode", "Consolas"); user_pref("font.name.monospace.x-western", "Consolas"); user_pref("font.name.sans-serif.el", "Calibri"); user_pref("font.name.sans-serif.tr", "Calibri"); user_pref("font.name.sans-serif.x-baltic", "Calibri"); user_pref("font.name.sans-serif.x-central-euro", "Calibri"); user_pref("font.name.sans-serif.x-cyrillic", "Calibri"); user_pref("font.name.sans-serif.x-unicode", "Calibri"); user_pref("font.name.sans-serif.x-western", "Calibri"); user_pref("font.name.serif.el", "Cambria"); user_pref("font.name.serif.tr", "Cambria"); user_pref("font.name.serif.x-baltic", "Cambria"); user_pref("font.name.serif.x-central-euro", "Cambria"); user_pref("font.name.serif.x-cyrillic", "Cambria"); user_pref("font.name.serif.x-unicode", "Cambria"); user_pref("font.name.serif.x-western", "Cambria"); user_pref("font.size.fixed.el", 14); user_pref("font.size.fixed.tr", 14); user_pref("font.size.fixed.x-baltic", 14); user_pref("font.size.fixed.x-central-euro", 14); user_pref("font.size.fixed.x-cyrillic", 14); user_pref("font.size.fixed.x-unicode", 14); user_pref("font.size.fixed.x-western", 14); user_pref("font.size.variable.el", 17); user_pref("font.size.variable.tr", 17); user_pref("font.size.variable.x-baltic", 17); user_pref("font.size.variable.x-central-euro", 17); user_pref("font.size.variable.x-cyrillic", 17); user_pref("font.size.variable.x-unicode", 17); user_pref("font.size.variable.x-western", 14); user_pref("idle.lastDailyNotification", 1545407520); user_pref("intl.charsetmenu.mailview.cache", "ISO-8859-15, windows-1252, KOI8-R, ISO-8859-1, UTF-8"); user_pref("mail.ab_remote_content.migrated", 1); user_pref("mail.account.account11.identities", "id10"); user_pref("mail.account.account11.server", "server11"); user_pref("mail.account.account13.identities", "id12"); user_pref("mail.account.account13.server", "server13"); user_pref("mail.account.account2.server", "server2"); user_pref("mail.account.account20.server", "server20"); user_pref("mail.account.account21.identities", "id1"); user_pref("mail.account.account21.server", "server1"); user_pref("mail.account.account22.identities", "id2"); user_pref("mail.account.account22.server", "server3"); user_pref("mail.account.account23.identities", "id3"); user_pref("mail.account.account23.server", "server4"); user_pref("mail.account.account24.identities", "id4"); user_pref("mail.account.account24.server", "server5"); user_pref("mail.account.account25.identities", "id5"); user_pref("mail.account.account25.server", "server6"); user_pref("mail.account.account26.identities", "id6"); user_pref("mail.account.account26.server", "server7"); user_pref("mail.account.account27.identities", "id7"); user_pref("mail.account.account27.server", "server8"); user_pref("mail.account.account28.identities", "id8"); user_pref("mail.account.account28.server", "server9"); user_pref("mail.account.lastKey", 29); user_pref("mail.accountmanager.accounts", "account2,account11,account13,account20,account21,account22,account23,account24,account25,account26,account27,account28"); user_pref("mail.accountmanager.defaultaccount", "account11"); user_pref("mail.accountmanager.localfoldersserver", "server2"); user_pref("mail.append_preconfig_smtpservers.version", 2); user_pref("mail.attachment.store.version", 1); user_pref("mail.citation_color", "#000066"); user_pref("mail.compose.attach.dir", "C:\\Users\\ITR\\Downloads"); user_pref("mail.compose.autosave", false); user_pref("mail.compose.big_attachments.notify", false); user_pref("mail.default_charsets.migrated", 1); user_pref("mail.default_html_action", 1); user_pref("mail.displayname.version", 604); user_pref("mail.folder.views.version", 1); user_pref("mail.font.windows.version", 2); user_pref("mail.identity.id1.archive_folder", "mailbox://grahame%40my-finca.com@mail.my-finca.com/Archives"); user_pref("mail.identity.id1.doBcc", false); user_pref("mail.identity.id1.draft_folder",

Something is amiss here. I did a full duplication of your issue. Are you looking at the prefs file for the active profile? You can verify by looking at the c:\users\<yourid>\appdata\roaming\thunderbird\profiles.ini to get the name of active profile.

Hi, looks as though there is another profile but with no layout.css

// Mozilla User Preferences

// DO NOT EDIT THIS FILE. // // If you make changes to this file while the application is running, // the changes will be overwritten when the application exits. // // To change a preference value, you can either: // - modify it via the UI (e.g. via about:config in the browser); or // - set it within a user.js file in your profile.

user_pref("app.update.auto.migrated", true); user_pref("app.update.download.attempts", 0); user_pref("app.update.lastUpdateTime.addon-background-update-timer", 1606913797); user_pref("app.update.lastUpdateTime.background-update-timer", 1606914037); user_pref("app.update.lastUpdateTime.blocklist-background-update-timer", 1606913917); user_pref("app.update.lastUpdateTime.search-engine-update-timer", 1606767314); user_pref("app.update.lastUpdateTime.services-settings-poll-changes", 1606864125); user_pref("app.update.lastUpdateTime.xpi-signature-verification", 1606914157); user_pref("app.update.migrated.updateDir2.8216C80C92C4E828", true); user_pref("browser.cache.disk.amount_written", 44348); user_pref("browser.cache.disk.capacity", 1048576); user_pref("browser.cache.disk.filesystem_reported", 1); user_pref("browser.launcherProcess.enabled", true); user_pref("browser.search.region", "ES"); user_pref("calendar.list.sortOrder", "58a17597-2ac3-4611-9b14-cfe4c74eae42"); user_pref("calendar.registry.58a17597-2ac3-4611-9b14-cfe4c74eae42.calendar-main-default", true); user_pref("calendar.registry.58a17597-2ac3-4611-9b14-cfe4c74eae42.calendar-main-in-composite", true); user_pref("calendar.registry.58a17597-2ac3-4611-9b14-cfe4c74eae42.name", "Home"); user_pref("calendar.registry.58a17597-2ac3-4611-9b14-cfe4c74eae42.type", "storage"); user_pref("calendar.registry.58a17597-2ac3-4611-9b14-cfe4c74eae42.uri", "moz-storage-calendar://"); user_pref("calendar.timezone.local", "Europe/Paris"); user_pref("calendar.ui.version", 3); user_pref("extensions.activeThemeID", "default-theme@mozilla.org"); user_pref("extensions.blocklist.lastModified", "Mon, 23 Nov 2020 15:46:42 GMT"); user_pref("extensions.blocklist.pingCountTotal", 2); user_pref("extensions.blocklist.pingCountVersion", 2); user_pref("extensions.databaseSchema", 31); user_pref("extensions.getAddons.cache.lastUpdate", 1606913797); user_pref("extensions.getAddons.databaseSchema", 5); user_pref("extensions.incognito.migrated", true); user_pref("extensions.installedDistroAddon.{e2fda1a4-762b-4020-b5ad-a41df1933103}", true); user_pref("extensions.lastAppBuildId", "20190909201201"); user_pref("extensions.lastAppVersion", "68.1.0"); user_pref("extensions.lastPlatformVersion", "68.1.0"); user_pref("extensions.pendingOperations", false); user_pref("extensions.systemAddonSet", "{\"schema\":1,\"addons\":{}}"); user_pref("extensions.webextensions.uuids", "{\"{e2fda1a4-762b-4020-b5ad-a41df1933103}\":\"a5d18d5b-656d-4e9b-b23f-0ceef782768f\",\"wetransfer@extensions.thunderbird.net\":\"4dfcdf45-4622-46f2-87f3-a073564f3c1f\",\"default-theme@mozilla.org\":\"be63beee-c913-4b05-8aa7-66a3317cd57c\",\"google@search.mozilla.org\":\"a77ef9f5-38ba-458d-a7a7-777a5071a3fb\",\"bing@search.mozilla.org\":\"a9828948-fd48-48a2-ac34-699b9a604f2d\",\"amazon@search.mozilla.org\":\"c6a48ca6-05f2-4c61-8665-36e722f6ab97\",\"chambers-en-GB@search.mozilla.org\":\"b9fcc909-306e-473e-b3a6-22859f640220\",\"ddg@search.mozilla.org\":\"1c7608d4-e2b2-44e5-9e5e-b5d574c71358\",\"twitter@search.mozilla.org\":\"bf70a0d6-9c9b-4c4a-93d0-a789503c983c\",\"wikipedia@search.mozilla.org\":\"cbca0956-0652-4152-a0ad-907fd1516c5c\"}"); user_pref("idle.lastDailyNotification", 1606917273); user_pref("layers.mlgpu.sanity-test-failed", false); user_pref("mail.ab_remote_content.migrated", 1); user_pref("mail.append_preconfig_smtpservers.version", 2); user_pref("mail.default_charsets.migrated", 1); user_pref("mail.rights.version", 1); user_pref("mail.ui-rdf.version", 17); user_pref("mailnews.database.global.datastore.id", "6cc9d787-386e-4861-a75a-b3c96fbe7b9"); user_pref("mailnews.quotingPrefs.version", 1); user_pref("mailnews.start_page_override.mstone", "68.1.0"); user_pref("mailnews.tags.$label1.color", "#FF0000"); user_pref("mailnews.tags.$label1.tag", "Important"); user_pref("mailnews.tags.$label2.color", "#FF9900"); user_pref("mailnews.tags.$label2.tag", "Work"); user_pref("mailnews.tags.$label3.color", "#009900"); user_pref("mailnews.tags.$label3.tag", "Personal"); user_pref("mailnews.tags.$label4.color", "#3333FF"); user_pref("mailnews.tags.$label4.tag", "To Do"); user_pref("mailnews.tags.$label5.color", "#993399"); user_pref("mailnews.tags.$label5.tag", "Later"); user_pref("mailnews.tags.version", 2); user_pref("media.gmp.storage.version.observed", 1); user_pref("media.hardware-video-decoding.failed", false); user_pref("places.database.lastMaintenance", 1606917273); user_pref("places.history.expiration.transient_current_max_pages", 112348); user_pref("sanity-test.advanced-layers", true); user_pref("sanity-test.device-id", "0x11b6"); user_pref("sanity-test.driver-version", "22.21.13.8573"); user_pref("sanity-test.running", false); user_pref("sanity-test.version", "20190909201201"); user_pref("security.sandbox.plugin.tempDirSuffix", "{1cce22d2-f9df-427e-b8f2-875447a3adde}"); user_pref("services.blocklist.pinning.checked", 1606864125); user_pref("services.settings.clock_skew_seconds", -1); user_pref("services.settings.last_etag", "\"1606852681886\""); user_pref("services.settings.last_update_seconds", 1606864125); user_pref("services.settings.main.hijack-blocklists.last_check", 1606864125); user_pref("services.settings.main.language-dictionaries.last_check", 1606864125); user_pref("services.settings.main.sites-classification.last_check", 1606864125); user_pref("services.settings.security.onecrl.checked", 1606864125); user_pref("signon.importedFromSqlite", true); user_pref("storage.vacuum.last.index", 0); user_pref("storage.vacuum.last.places.sqlite", 1606917273); user_pref("toolkit.telemetry.cachedClientID", "4065e336-db0a-42e4-9efb-5f56a58dd86a"); user_pref("ui.osk.debug.keyboardDisplayReason", "IKPOS: Touch screen not found.");

I added "user_pref("layout.css.devPixelsPerPx", "1.5");" to the bottom of this profile, saved and started TB, but no change..

Okay, add the entry while thunderbird is not running. now start thunderbird click help>moretroubleshootinginformation scroll down to 'profile folder' and click 'open profile' exit thunderbird and you are now in the profile. open the pref file and check contents. you should see the layout entry.

Yes, I did add it when tb was not running and nothing changed as you can see from attached screen sot.

So what am I supposed to do with TB to get it functioning again correctly? Can I re install and keep all accounts and other details? Thanks

Let's try one more thing, since I find it very hard to understand that this is happening. - exit Thunderbird - create a simple text file with name of user.js with these lines:

    // Set overall font size  ###   <== this line is optional, just for documentation
    user_pref("layout.css.devPixelsPerPx", "1.5");

- copy the user.js file into the profile - restart thunderbird

If all goes well Thunderbird will add that to the prefs file and change the font size. I did a test myself, but I still have this fear that you may be looking at wrong prefs file

Hello David Sadly no change Just to confirm the address of the profile folder... C:\Users\GP\AppData\Roaming\Thunderbird\Profiles\x9j3qboz.default-release

I have attached a snapshot of my file system if that may help.. Thanks

Puzzling. Your screenshot indicates the Prefs file was last updated five days ago. That still indicates that this may be the wrong profile. Have you confirmed that the appdata\thunderbird\profiles.ini is pointing to this folder? I know I may be wrong, but to see Thunderbird ignore the prefs file is unusual. I also noticed that no files have been updated since 2020, indicating this profile may no longer be used.

Okay well firstly I did try out TB in 2020 sometime but still carried on with Win 7 mail as I preferred it. I changed my laptop probably nearly 2 years ago now, it had win10 and couldn't run winmail.... Tried Mailbird, didn't go a lot on that and then must have been around summertime 2022 changed to TB. Over the period I have had notifications that it was autoupdating and I too was surprised not to see later files in the system! So I did a search with Listify which came up with C:\Users\Administrator\AppData\Roaming\Thunderbird\Profiles\xuf55woa.default-release BINGO... Layout was at 10, now changed to 1.2 and perfect.... Very many thanks for your help David!!

Awesome! Free drinks all around!!! Sanity prevails. I'm very pleased you were able to fix this.

NOTE: layout.css.devPixelsPerPx is supported by Firefox, but is deprecated (no longer supported) for Thunderbird starting at version 115. Anything other than the default -1.0 may cause problems or inconsistent results now or in the future. Reference: https://support.mozilla.org/en-US/kb/thunderbird-115-supernova-faq#w_why-are-the-fonts-still-too-large-or-too-small-after-i-changed-the-density-and-font-size